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SELECT  METHODS 


IN 


FOOD  ANALYSIS 


HENRY    LEFFMANN,  A.M.,  M.D.,  PH.D. 

AND 

WILLIAM  BEAM,  A.M.,  M.D.,  F.LC. 


SE.COND    EDITION,    REVISED    AND    ENLARGED 


•CClftb  One  Plate  an& 
54  ©tber  f  llustratlons 


PHILADELPHIA 

P.   BLAKISTON'S  SON   &  CO. 

I0I2    WALNUT    STREET 
1905 


-v' 


V 


Copyright,  1905,  by  P.  Blakiston's  Son  &  Co. 


PRESS    OF 
.    FELL    COMPANY 
HILADELPHIA 


PREFACE  TO  SECOND  EDITION 


The  rapid  sale  of  the  first  edition  of  this  work,  and  the  favor- 
able opinions  expressed  in  reviews  and  correspondence,  have 
encouraged  the  authors  to  prepare  a  second  edition,  which  it  is 
hoped  will  be  worthy  of  the  position  attained  by  the  first.  The 
preparation  of  the  second  edition  has  been  considerably  de- 
layed, and  in  the  interval  much  progress  has  been  made  in  the 
field.  American  work  is  rapidly  becoming  the  leader  in  food- 
analysis.  The  excellent  equipment  of  the  laboratories  of  the 
Department  of  Agriculture  at  Washington,  supplemented  by 
more  than  two-score  of  State  experiment  stations,  and  by  hun- 
dreds of  investigators,  connected  with  Boards  of  Health  and 
Food  Commissioners,  enables  every  problem  to  be  submitted  to 
prompt  and  searching  inquiry.  We  have  endeavored  to  utilize 
this  material  fully.  It  is  to  be  regretted  that  the  publication 
of  these  investigations  is  still  unsatisfactory,  important  results 
often  appearing  in  bulletins  of  local  circulation  and  limited 
editions.  It  is  to  be  hoped  that  some  system  of  international 
publication,  easy  of  access,  will  be  instituted. 

In  the  present  edition  much  alteration  has  been  made.  Many 
paragraphs  have  been  cancelled  and  much  new  matter  inserted. 
Among  the  additions  are:  Detailed  descriptions  of  special 
arrangements  for  polarimetry,  distillation  and  extraction;  new 
processes  for  detection  of  natural  colors  used  as  substitutes  for 
fruit  and  egg-colors;  improvements  in  detection  of  formaldehyde, 
abrastol  and  saccharin;  rapid  methods  for  examination  of 
vanilla  and  lemon  extracts,  and  for  the  determination  of  fat  in 
condensed  milk  and  cereal  foods;   determination  of  boric  acid  in 


iii:^5S 


IV  PREFACE   TO   THE    SECOND   EDITION 

fruit-juices;  analytic  data  in  regard  to  fruit-juices,  jams  and 
jellies;  detection  of  palm  oil  in  oleomargarin,  and  many  minor 
modifications  of  tests  and  processes  intended  to  simplify  or  ex- 
pedite analysis. 

The  purpose  of  the  book  has  not  been  modified.  It  is  for  the 
practical  worker  in  the  detection  of  food  adulteration.  No 
space  has  been  given  to  discussion  of  the  effects  of  adulteration, 
nor  to  the  principles  to  be  observed  in  the  establishment  of 
food-standards,  or  in  framing  or  administering  food-laws. 
These  are  not  matters  for  the  analyst.  The  standards  pub- 
lished by  the  U.  S.  Government  have  been  included  as  official 
interpretations  of  analytic  data. 

All  temperatures  are  centigrade.  Unless  otherwise  noted, 
all  readings  of  scale  or  arc  are  positive;  sulfuric,  nitric  and 
hydrochloric  acids  and  ammonium  hydroxid  are  the  standard 
concentrated  pure  grades  of  these  reagents;  alcohol  is  95  per 
cent. 

Philadelphia,  May,  1905. 


ADDITIONS  AND  CORRECTIONS 

Page  64,  after  line  3,  insert  "For  special  methods  for  detection  and  determin- 
ation of  aluminum,  see  pages  378  and  386." 

Page  79,  after  line  4,  insert  "Aluminum  oxyacetate  is  sometimes  used  as  a 
meat-preservative;  see  pages  378  and  386," 

Page  139,  line  3,  insert  after  "  Hiibl  "  the  reference-figure  ^^. 

Paj^e  140,  line  16  from  bottom,  for  ^^  read  ^^. 

Page  349,  line  13,  for  "  lo  per  cent."  read  "  16  per  cent." 


NOTE  SPECIAL  PAGE  FOLLOWING  INDEX 


CONTENTS 


ANALYTIC  METHODS 
Physical  Data:  pace 
Specific    Gravity — Melting    and    Solidifying    Points — Boiling- 
point  —  Polarimetry  —  Spectroscopy  —  Fluorescence  —  Micros- 
copy,           1-26 

Chemical  Data: 

Water  and  Fixed  Solids  (Extract) — Nitrogen — Crude  Fiber — 
Ash — Extraction  with  Miscible  Solvents — Extraction  with  Im- 
miscible Solvents — Distillation  and  Sublimation — Apparatus 
and  Chemicals, 27-56 

APPLIED  ANALYSIS 
General  Methods: 

Poisonous  Metals — Colors — Preservatives, 57-86 

Special  Methods: 

3tarch,    Flours,    and   Meals — Bread — Leavening   Materials — 

Sugars — Honey — Candies  and  Confections, 86-136 

Fats  and  Oils:  lodin  Number — Volatile  Acids — Saponification 
Value — Acid  Value — Solubility  in  Acetic  Acid — Thermal  Reac- 
tion with  Sulfuric  Acid — Specific  Temperature  Reaction — 
Bromin  Thermal  Value — Elaidin  Test — Refractive  Index — 
Soluble  and  Insoluble  Acids — Cholesterol  and  Analogs — 
Acetyl  Value — Unsaponifiable  Matter — Analytic  Data — Special 

Tests, 137-168 

Olive  Oil — Cottonseed  Oil — Maize  Oil — Arachis  Oil^-Sesame 
Oil — Rape  Oil — Coconut  Oil — Cacao-butter — Lard — Butter- 
fat, 168-189 

Milk  and  Milk  Prodticts:    Milk — Condensed  Milk — Butter — 

Cheese — Fermented  Milk  Products, 190-251 

Non-alcoholic  Beverages:  Tea — Coffee — Cacao, 251-282 

Condiments  and  Spices:  Vinegar — Pepper — Long  Pepper — 
Cayenne  Pepper — Ginger — Nutmeg — Mace — Allspice — Cinna- 
mon— Cloves — Mustard — Flavoring  Extracts — Fruit-products 
Table  Accessories  and  Desserts — Egg-substitutes, 282-336 

V 


VI  CONTENTS 

Special  Methods  {Continued):  page 
Alcoholic  Beverages:    Cider — Spirits — Whiskey — Brandy — Gin 
— Rum — Malt    Liquors — ^Wine — Alcohol    Tables — Malt    Ex- 
tracts,    337-3 72 

Flesh  Foods:  Meats — Meat-extracts, 373-385 


Appendix.     Tables — References, 386-3S8 

Index. 


FOOD   ANALYSIS 


ANALYTIC  METHODS 

PHYSICAL  DATA 

Specific  Gravity. 

In  food  analysis,  determination  of  specific  gravity  of  solids  is 
rarely  made.     Fats  are  usually  tested  in  the  melted  condition. 

The  following  method  for  solid  fats,  due  to  Hager,  is  suita- 
ble for  small  amounts  of  material :  The  sample  is  melted  and 
allowed  to  drop  slowly  from  the  height  of  aboilt  3  centimeters 
into  some  cold  alcohol  in  a  dish.  The  globules  thus  obtained 
are  placed  in  diluted  alcohol  at  15.5°,  the  strength  of  which 
is  so  adjusted  that  the  globules  float  in  any  part  of  the  liquid. 
The  specific  gravity  of  the  liquid  is  then  determined;  it  is,  of 
course,  the  same  as  that  of  the  globules.  Many  substances 
when  cooled  suddenly  are  liable  to  have  abnormal  density, 
hence  it  is  preferable,  as  noted  by  Allen,  to  use  fragments 
cut  from  a  solid  mass  cooled  under  normal  conditions  and 
allowed  to  stand  at  least  twenty-four  hours. 

The  specific  gravity  of  a  liquid  is  generally  expressed  by 
comparison  with  water.  Confusion  and  inconvenience  have 
arisen  from  the  fact  that  results  have  been  referred  to  water  at 
different  temperatures  as  unity.  It  is  becoming  customary 
to  express,  as  is  proper,  the  temperatures  of  observation  and 
comparison.  ^^  indicates  a  determination  at  100°  and  com- 
3  I 


2  FOOD   ANALYSIS 

parison  with  water  at  15.5°  as  unity.     It  is  best  to  compare 
the  substance  and  the  standard  at  the  same  temperature. 

Pyknometer  or  Specific- gravity  Bottle. — This  is  an  accurate, 
generally  applicable  means  of  determining  specific  gravity.  It 
is  a  bottle  with  a  perforated  stopper,  adjusted  to  hold  a 
certain  weight  of  water  at  a  standard  temperature,  usually 
15.5°.  Bottles  as  sold  are  often  inaccurate.  The  weight  of 
water  that  a  bottle  holds  should  be  carefully  determined. 

E.  R.  Squibb  devised  a  convenient  form  of  pyknometer  (fig- 
ure i)  which  permits  the  determination  to  be  made  at  any 
_  temperature  between  o  and  25°,  and  compared 
with  water  at  the  same  temperature.  The  bottle 
should  hold  100  grams  of  recently-boiled  distilled 
water  at  20°  at  about  58  on  a  scale  of  o  to  100. 
In  weighing  the  water  into  the  bottle,  the  fine  adjust- 
ment to  o.ooi  gram  is  made  by  use  of  narrow  strips 
of  blotting-paper  that  will  pass  easily  down  the  bore 
of  the  graduated  stem.  When  the  100  grams  are  in 
the  bottle,  and  the  column  stands  between  50  and 
65  divisions  of  the  scale,  the  stopper  is  put  in,  a 
leaden  ring  is  put  on  the  neck,  and  the  whole  im- 
■pj^j  J  mersed  in  a  bath  of  broken  ice  and  water  until 
the  column  of  water  comes  to  rest.  It  should  then 
read  at  zero  of  the  scale,  or  not  much  above  it,  and  the  read- 
ing should  be  noted.  If  it  reads  below  zero,  the  bottle  is  too 
large,  and  the  stopper  part  of  the  stem  must  be  ground  farther 
into  the  bottle  neck,  until  the  reading,  on  new  trial,  brings  the 
column  a  little  above  zero.  The  bottle  is  then  put  into  a  bath 
at  25°  and  kept  there,  with  stirring  of  the  bath,  until  the 
column  comes  to  rest,  when  it  should  read  somewhere  from 
90  to  TOO  of  the  scale.  Should  it  read  above  100,  while  the 
lower  limit  is  as  far  above  the  zero,  the  bottle  is  too  small,  and 
the  end  of  the  stopper  must  be  ground  off  until  the  reading  of 
the  column  is  within  the  graduations  at  both  ends  of  the  scale. 


SPECIFIC  GRAVITY 


Sprengel  Tube. — This  is  a  form  of  pyknometer  with  which 
a  high  degree  of  accuracy  is  attainable.  It  is  especially  suita- 
ble for  determinations  at  the  boiling-point  of  water.  It  con- 
sists (figure  2)  essentially  of  a  thin  glass  U-tube  terminating 
in  two  capillary  ends  bent  at  right  angles  and  each  provided 
with  a  ground  cap.  One  of  these  capillary  tubes  must  have 
a  smaller  caliber  than  the  other — not  larger  than  0.25  mm. 
The  larger  tube  should  bear  a  mark  at  m.  The  tube  is  filled 
by  immersing  h  in  the  liquid  under  examination,  connecting 


"iW 


w 


Fig. 


Fig.  3. 


the  smaller  end  with  a  large  glass  bulb,  and  applying  suction 
to  the  latter  by  means  of  a  rubber  tube,  as  shown  in  figure  3. 
If  now  the  rubber  tube  be  closed,  the  glass  tube  will  fill  auto- 
matically. It  is  placed  in  water,  the  ends  being  allowed  to 
project,  and  the  water  is  brought  to  the  proper  temperature. 
A  conical  flask  may  be  used  to  contain  the  water,  the  ends 
of  the  Sprengel  tube  being  supported  by  the  neck.  The 
mouth  of  the  flask  should  be  loosely  covered.    As  the  Hquid 


4  FOOD  ANALYSIS 

expands  it  will  drop  from  the  larger  orifice.  When  this  ceases, 
the  liquid  is  adjusted  to  the  mark  at  m.  If  beyond  the  point, 
a  little  may  be  extracted  by  means  of  a  roll  of  paper.  The 
tube  is  then  taken  out  of  the  bath,  the  caps  adjusted,  the 
whole  thoroughly  dried,  allowed  to  cool,  and  weighed.  The 
same  operation  having  been  performed  with  distilled  water, 
the  calculation  of  the  specific  gravity  is  made  as  usual. 

Westphal   Balance. — This   affords   a   convenient   means   of 
determining  specific  gravity.     It  consists  of  a  delicate  steel- 


FlG.  4. 


yard  provided  with  a  counterpoised  plummet.  The  latter, 
being  immersed  in  the  liquid,  the  equilibrium  is  restored  by 
means  of  weights  or  riders,  the  value  of  which  is  directly  ex- 
pressed in  figures  for  the  specific  gravity  without  calculation. 
Thus,  the  rider  A'  is  of  such  a  weight  as  to  express  the  first 
decimal  place,  and  will  be  represented  by  any  of  the  figures 
from  o  to  9  according  to  its  position  on  the  beam..  Similarly 
the  riders  A,  B  and  C  furnish  the  figures  for  the  second,  third 
and  fourth  decimal  places  respectively.  The  weight  A^ 
used  in  the  case  of  liquids  heavier  than  water. 


is 


SPECIFIC  GRAVITY  5 

The  ordinary  form  of  Westphal  balance  is  untrustworthy, 
but  good  instruments  are  made  by  some  European  manu- 
facturers. 

The  principle  of  the  hydrostatic  balance  may  be  applied 
by  using  a  plummet  (that  sold  with  the  Westphal  balance 
will  serve)  with  the  ordinary  analytic  balance.  Test-tubes 
weighted  with  mercury  and  sealed  in  the  flame  may  also  be 
used.     The  plummet  is  suspended  to  the  hook  of  the  balance 


Fig.  5. 


Fig.  6. 


by  means  of  a  fine  platinum  wire.  The  specific  gravity  of  any 
liquid  may  be  determined  by  noting  the  loss  of  weight  of  the 
plummet  when  immersed  in  the  liquid  and  dividing  this  by 
the  loss  in  pure  water. 

If  the  determination  be  made  at  the  boiling-point  of  water, 
the  arrangements  shown  in  Figs.  5  and  6  may  be  employed. 
The  temperature  of  the  liquid  will  not  usually  rise  above  99°. 
This  may  be  done  with  a  hydrometer  or  balance,  if  the  cylin- 


6  FOOD  ANALYSIS 

der  containing  the  oil  be  kept  for  a  sufficient  time  in  boiling 
water.  With  the  Sprengel  tube  high  accuracy  may  be  ob- 
tained. The  weight  of  the  Sprengel  tube  and  that  of  water 
contained  at  15.5°  being  known,  the  tube  should  be  com- 
pletely filled  with  the  oil,  by  immersing  one  of  the  orifices  in 
the  liquid  and  sucking  at  the  other.  The  tube  is  placed  in  a 
conical  flask  containing  water  which  is  kept  actively  boiling,  a 
porcelain  crucible-cover  being  placed  over  the  mouth  of  the 
flask.  The  oil  expands  and  drops  from  the  orifices.  When 
this  ceases,  the  oil  adhering  to  the  outside  is  removed  by  the 
cautious  use  of  filter-paper,  the  tube  removed,  wiped  dry, 
cooled,  and  weighed.  The  weight  of  the  contents  divided  by 
the  weight  of  water  contained  at  15.5°  will  give  the  specific 
gravity  at  the  temperature  attained  compared  with  water  at 
15.5°.  When  the  amount  of  material  is  sufficient,  the  deter- 
mination may  be  made  by  use  of  the  plummet,  employing  a 
cylindrical  bath  with  two  orifices.  One  of  these  is  fitted  with 
an  upright  tube  for  conveying  the  steam  away  from  the  neigh- 
borhood of  the  balance;  into  the  other  a  test-tube,  15  cm.  in 
length  and  2.5  cm.  in  diameter,  fits  tightly,  the  joint  being 
made  perfect  by  cork  or  india-rubber.  The  test-tube  is  filled 
with  the  substance  to  be  tested,  and  the  plummet  immersed 
in  it.  The  water  in  the  outer  vessel  is  then  kept  in  constant 
ebullition,  until  a  thermometer,  with  which  the  oil  is  repeat- 
edly stirred,  indicates  a  constant  temperature,  when  the  plum- 
met is  attached  to  the  lever  of  the  balance,  and  counterpoised. 
For  temperatures  higher  than  100°  glycerol  or  paraffin  may 
be  used,  but  considerable  care  is  required  in  such  cases. 

Hydrometers  are  much  used  for  the  determination  of  the 
specific  gravity  of  liquids,  but  the  indications  are  less  reliable 
than  by  the  methods  described  above.  The  instruments  as 
furnished  are  often  not  accurately  graduated,  and  the  zero 
point,  at  least,  should  be  verified  by  immersing  in  distilled 
water  at  a  standard  temperature.     Sensitive  hydrometers  with 


MELTING   AND  SOLIDIFYING  POINTS  7 

slender  stems,  accurately  graduated,  are  now  obtainable. 
These  are  capable  of  furnishing  good  results.  Care  should 
be  taken  to  make  the  reading  at  the  top,  center  or  bottom 
of  the  meniscus  according  to  the  method  used  in  the  grad- 
uation of  the  instrument.  Instruments  intended  for  use  with 
opaque  liquids  should  be  graduated  to  be  read  at  the  top  of 
the  meniscus. 

The  actual  specific  gravity  of  any  substance  is  the  ratio  of 
its  density  at  a  given  temperature  to  that  of  water  at  the  same 
temperature.  Statements  made  upon  any  other  basis  than  this 
may  be  converted  into  actual  specific  gravity  by  calculation 
from  the  table  of  density  of  water  given  in  the  appendix. 
Thus,  a  determination  of  specific  gravity  of  0.8000  at  7^ 
may  be  converted  into  actual  specific  gravity  (^)  as  follows: 

Density  of  water  at    15°  =  0.99916. 
100°  =  0.95866. 
too"  100° 

is"  100° 

Therefore,  95866  :  99916  :  :  0.8000  :  0.8337  (actual  specific  gravity  at  100°). 

Melting  and  Solidifying  Points. 

The  determination  of  these  is  often  difficult.  Many  sub- 
stances, especially  fats,  assume  conditions  exhibiting  abnormal 
melting-points,  and  also  frequently  solidify  at  a  temperature 
very  different  from  that  at  which  they  melt.  If,  in  the  prep- 
aration of  any  substance  for  determining  its  melting-point,  it 
is  necessary  to  make  a  previous  fusion,  the  mass  should  be 
allowed  to  rest  not  less  than  twenty-four  hours  after  solidifi- 
cation before  making  the  experiment.  Chemists  disagree  as  to 
whether  the  melting-point  should  be  considered  to  be  that  at 
which  the  substance  begins  to  be  liquid  or  that  at  which  the 
liquid  is  perfectly  clear.  Ordinary  thermometers  are  frequently 
inaccurate,  the  error  amounting  to  a  degree  or  more.  No  ob- 
servations in  which  precision  is  required  should  be  made  with 
unverified  instruments. 


8 


FOOD  ANALYSIS 


The  following  method  for  determining  melting-points  is 
suitable  for  many  technical  purposes.  By  substituting  strong 
brine  or  glycerol  for  the  water  in  the  bath  observations  may 
be  made  at  temperatures  beyond  the  limits  of  o°  and  ioo°: 

The  substance  is  heated  to  a  temperature  slightly  above  its 


Fig.  7. 


Fig.  8. 


fusing-point,  drawn  into  a  very  narrow  glass  tube,  and  allowed 
to  solidify  for  not  less  than  twenty-four  hours.  The  tube,  open 
at  both  ends,  is  attached  by  a  wire  or  rubber  ring  to  a. thermom- 
eter so  that  the  part  containing  the  substance  is  close  to  the 
bulb.  The  apparatus,  immersed  in  water,  is  heated  at  a  rate 
not  exceeding  0.5°  per  minute  until  fusion  takes  place,  when 


MELTING   AND   SOLIDIFYING   POINTS  9 

the  temperature  is  noted.  The  temperature  is  allowed  to  fall 
and  the  point  at  which  the  substance  becomes  solid  is  also 
observed.  To  insure  uniform  and  gradual  heating,  it  is  neces- 
sary to  immerse  the  vessel  containing  the  thermometer  and 
tube  in  another  larger  vessel  filled  with  water.  Allen  sug- 
gests a  flask  of  which  the  neck  has  been  cut  off,  as  shown  in 
figure  7.  A  neater  form  of  apparatus  is  shown  in  figure  8, 
from  "Richter's  Organic  Chemistry." 

The  two  following  methods  are  especially  adapted  to  the 
examination  of  fats  and  waxes.  The  A.  O.  A.  C.  method  dis- 
regards the  abnormal  condition  of  recently-solidified  masses : 

A.  O.  A.  C.  Method. — A  mixture  of  alcohol  and  water  of 
the  same  specific  gravity  as  the  sample  is  prepared  in  the  fol- 
lowing manner:  Separate  portions  of  distilled  water  and  95 
per  cent,  alcohol  are  boiled  for  10  minutes.  The  water  is 
poured,  while  still  hot,  into  the  test-tube  described  below 
until  it  is  nearly  half  full.  The  test-tube  is  nearly  filled  with 
the  hot  alcohol,  which  is  carefully  poured  down  the  side  of 
the  inclined  tube  to  avoid  too  much  mixing.  If  the  alcohol 
is  added  when  water  is  cold,  the  mixture  will  contain  air- 
bubbles  and  be  unfit  for  use. 

The  apparatus  (Fig.  9)  consists  of:  A  thermometer  reading 
easily  and  accurately  to  tenths  of  a  degree;  a  cathetometer 
for  reading  the  thermometer  (this  may  be  substituted  by  an 
eyeglass  if  held  steadily  and  properly  adjusted);  a  thermom- 
eter; a  tall  beaker  35  cm.  high  and  10  cm.  in  diameter;  a 
test-tube  30  cm.  long  and  3.5  cm.  in  diameter;  a  stand  for 
supporting  the  apparatus;  some  method  of  stirring  the  water 
in  the  beaker  (for  example,  a  rubber  blowing-bulb  and  a  glass 
tube  extending  to  near  the  bottom  of  the  beaker). 

The  melted  and  filtered  fat  is  allowed  to  fall  from  a  drop- 
ping-tube  from  a  height  of  from  15  to  20  cm.  on  a  smooth 
piece  of  ice  floating  in  recently-boiled  distilled  water.  Disks 
from  I  to  1.5  cm.  in  diameter,  and  weighing  about  200  mg., 


10 


FOOD  ANALYSIS 


are  formed.  Pressing  the  ice  under  the  water  the  disks  float 
on  the  surface,  and  are  easily  removed  with  a  steel  spatula, 
cooled  in  the  ice-water  before  using.     The  test-tube  contain- 


FiG.  9. 


ing  the  alcohol  and  water  is  placed  in  a  tall  beaker  containing 
water  and  ice,  until  cold.  The  disk  of  fat  is  then  dropped 
into  the  tube  from  the  spatula  and  at  once  sinks  to  the  part 
of  the  tube  where  the  density  of  the  diluted  alcohol  is  exactly 


MELTING  AND   SOLIDIFYING  POINTS  II 

equivalent  to  its  own.  The  delicate  thermometer  is  placed 
in  the  test-tube  and  lowered  until  the  bulb  is  just  above  the 
disk.  In  order  to  secure  an  even  temperature  in  all  parts  of 
the  alcohol  mixture  in  the  vicinity  of  the  disk,  the  thermom- 
eter is  used  as  a  stirrer.  The  disk  having  been  placed  in  posi- 
tion, the  water  in  the  beaker  is  slowly  heated  and  kept  con- 
stantly stirred  by  means  of  the  blowing  apparatus  already 
described.  When  the  temperature  of  the  alcohol-water  mix- 
ture rises  to  about  6°  below  the  melting-point,  the  disk  of 
fat  begins  to  shrivel  and  gradually  rolls  up  into  an  irregular 
mass.  The  thermometer  is  lowered  until  the  fat  particle  is 
even  with  the  center  of  the  bulb.  The  bulb  of  the  thermom- 
eter should  be  small,  so  as  to  indicate  only  the  temperature 
of  the  mixture  near  the  fat.  A  gentle  rotatory  movement 
should  be  given  to  the  thermometer  bulb.  The  rise  of  tem- 
perature should  be  so  regulated  that  the  last  2°  of  increment 
require  about  ten  minutes.  The  mass  of  fat  gradually  ap- 
proaches the  form  of  a  sphere,  and  when  it  is  sensibly  so  the 
reading  of  the  thermometer  is  taken.  As  soon  as  the  tem- 
perature is  taken  the  test-tube  is  removed  from  the  bath  and 
placed  again  in  the  cooler.  A  second  tube,  containing  alcohol 
and  water,  is  at  once  placed  in  the  bath.  The  test-tube  (ice- 
water  having  been  used  as  a  cooler)  is  of  low  enough  tem- 
perature to  cool  the  bath  sufficiently.  After  the  first  deter- 
mination, which  should  be  only  a  trial,  the  temperature  of 
the  bath  should  be  so  regulated  as  to  reach  a  maximum  of 
about  1.5°  above  the  melting-point  of  the  fat  under  examina- 
tion. If  the  edge  of  the  disk  touches  the  sides  of  the  tube 
a  new  trial  should  be  made.  Second  and  third  results  should 
show  a  near  agreement. 

TiTER-TEST. — To  eliminate  error  in  determining  melting- 
points  of  intimate  mixtures,  such  as  commercial  fats  and  waxes, 
the  titer-test,  proposed  by  Dalican,  has  been  largely  adopted. 

100  grams  of  the  fat  are  saponified,  the  fatty  acids  separated 


12 


FOOD  ANALYSIS 


by  addition  of  acid,  freed  from  water,  filtered  into  a  porcelain 
dish,  and  allowed  to  solidify  overnight  under  a  desiccator. 
The  mass  is  then  carefully  melted  in  an  air-bath  and  sufficient 
poured  into  a  test-tube  i6  cm.  long  and  3.5  cm.  in  diameter 
to  fill  the  tube  a  little  more  than  halfrfuU.  The  tube  is  then 
placed  in  a  suitable  flask,  say  of  2000  c.c.  capacity,  and  a  deli- 
cate thermometer,  indicating  one-fifth  of  a  degree,  inserted  so 
that  the  bulb  reaches  the  center  of  the  mass.  When  a 
few  crystals  appear  at  the  bottom  of  the  tube, 
the  mass  is  stirred  by  giving  the  thermometer 
a  rotatory  movement,  first  three  times  from 
right  to  left,  then  three  times  from  left  to  right, 
and  then  continuously,  by  a  quick  circular  move- 
ment of  the  thermometer,  without  allowing  it  to 
touch  the  side  of  the  vessel,  but  taking  care  that 
all  solidifying  portions,  as  they  form,  are  well 
stirred  in.  The  liquid  will  gradually  become 
cloudy  throughout,  and  the  thermometer  must  be 
observed  carefully.  At  first  the  temperature  will 
fall,  but  will  soon  rise  suddenly  a  few  tenths  of  a 
degree  and  reach  a  maximum  at  which  it  remains 
stationary  for  a  short  time  before  it  falls  again. 
This  point  is  called  the  ''titer"  or  sohdifying  point. 


Boiling-point. 

Fig.  10.  For  the  determination  of  boiling-point  the  ap- 

paratus of  Berthelot  is  convenient.  Figure  10, 
from  Traube's  '' Physico- Chemical  Methods,"  shows  the  con- 
struction. The  thermometer  is  inclosed  in  an  outer  tube,  so 
that  the  portion  of  the  scale  to  which  the  mercury  rises  is 
immersed  in  the  vapor.  If  this  be  not  done,  a  correction 
must  be  applied  for  the  error  produced  by  the  cooling  of  the 
thermometer  tube.  The  bulb  of  the  thermometer  does  not 
reach  into  the  liquid.     A  few  fragments  of  pumice-stone  or 


POLARIMETRY  1 3 

broken  clay  pipestems  will  prevent  bumping.  The  exit-tube 
at  the  lower  end  of  the  wide  tube  connects  with  a  condenser. 
The  barometric  pressure  must  always  be  noted  and  correction 
made  for  the  variation  from  the  standard  pressure,  760  mm., 
by  the  following  formula: 

B  =  B^  +  0.0375  (760 — ^P);  in  which 
B  is  the  boiling-point  at  normal  pressure, 
B^  the  observed  boiling-point, 
P  the  observed  pressure  in  millimeters. 

For  an  apparatus  designed  for  special  boiling-point  observa- 
tions see  under  ''AlcohoHc  Beverages." 

Polarimetry. 

Polarimeters  are  instruments  used  to  measure  the  extent 
and  direction  of  the  rotation  of  the  plane  of  polarized  light. 
They  consist  essentially  of  a  Nicol's  prism  as  polarizer,  a  tube 
carrying  the  substance  to  be  tested,  and  a  second  Nicol's 
prism,  or  analyzer,  by  which  the  extent  of  rotation  is  meas- 
ured. In  all  forms  some  condition  of  the  field  of  vision  is 
fixed  upon  as  the  zero  point,  and  the  rotation  of  the  analyzer 
or  other  manipulation  necessary  to  restore  this  standard  field 
affords  the  measurement  of  the  rotation  caused  by  the  inter- 
posed substance.  Several  types  of  instrument  have  been  de- 
vised, of  which  two  are  most  important.  In  one  form,  de- 
vised by  Soleil,  white  light  is  used  and  a  colored  field,  known 
as  the  transition  tint,  is  taken  as  the  zero  point.  In  the  other 
type  white  light  or  monochromatic  (yellow)  light  is  used  and 
the  zero  point  determined  by  equahzing  the  brightness  of  the 
field.  Instruments  of  the  first  form  are  unsatisfactory  by 
reason  of  the  difference  in  susceptibiUty  in  the  eyes  of  differ- 
ent person  to  color-contrasts.  The  instruments  of  the  second 
type,  commonly  designated  shadow  instruments  (more  cor- 
rectly, ''penumbral"),  are  now  more  generally  employed. 

In  the  Laurent  apparatus,  shown  in  figure  11,  the  mono- 


14 


FOOD  ANALYSIS 


chromatic  light  passes  through  the  collimating  lens  A  and  is 
polarized  by  the  Nicol's  prism  B,  which  is  so  placed  that  it  may 
be  moved,  on  its  axis,  over  a  small  arc  by  means  of  the  lever 
C  and  clamped  at  any  point;  by  this  the  brightness  of  the 
field  may  be  varied  and  the  sensitiveness  of  the  instrument  in- 
creased or  diminished  as  may  be  needed.  The  polarized  beam 
then  passes  through  a  quartz  plate  of  even  thickness,  cut  ex- 
actly parallel  to  the  optic  axis,  and  placed  so  that  it  covers  a 


Fig.  II. 


semicircle  of  the  field.  At  the  other  end  of  the  apparatus  is 
the  analyzing  prism  E  and  the  eye-piece  F  fixed  to  a  graduated 
disk.  This  combination  can  be  rotated  upon  its  axis  in  a  com- 
plete circle.  Attached  arms  carry  viev^-lenses  for  reading  the 
angle  of  rotation,  and  the  instrument  is  set  at  zero  by  an  in- 
dependent adjustment  by  which  the  analyzing  prism  is  rotated 
without  disturbing  the  position  of  the  graduated  disk.  Ver- 
niers are  provided  for  close  measurement.     The  monochro- 


POLARIMETRY  1 5 

matic  light  must  be  obtained  from  a  sodium  flame,  since  the 
thickness  of  the  quartz  plate  is  adjusted  to  these  rays. 

In  use,  the  tube  is  filled  with  water,  the  instrument  directed 
to  the  source  of  light,  and  the  adjusting  milled  head  turned 
until  the  disk  is  set  at  zero.  The  two  portions  of  the  field 
should  now  appear  equally  illuminated.  If  this  is  not  the  case, 
the  position  of  the  analyzer  must  be  altered  by  means  of  the 
independent  adjustment,  the  index  remaining  undisturbed  at 
the  zero  point. 

The  tube  is  filled  with  the  liquid  to  be  tested  and  again 
placed  in  the  instrument.  If  optically  active,  the  plane  of  the 
polarized  light  will  be  rotated  and  one-half  of  the  field  of 
observation  will  appear  darker.  The  extent  of  rotation,  which 
will  depend  upon  the  nature  of  the  substance  and  its  amount, 
is  measured  by  rotating  the  analyzer  to  the  right  or  left,  as 
the  case  may  be,  until  the  halves  of  the  field  become  equally 
illuminated. 

This  instrument  can  be  employed  to  measure  the  rotatory 
power  of  all  classes  of  substances,  but  other  forms  give  ac- 
curate indications  only  with  substances  which  have  the  same 
dispersive  power  as  quartz,  unless  monochromatic  light  be 
used.  In  the  Schmidt  and  Hansch  penumbral  instrument, 
the  division  of  the  field  is  obtained  by  a  special  construction 
of  the  polarizing  prism  and  the  restoration  is  accomplished  by 
the  adjustment  of  compensating  quartz-wedges  constructed  so 
as  to  produce  in  the  zero  position  no  rotation.  When  an 
optically  active  substance  is  interposed  in  the  path  of  the  ray, 
one  of  the  quartz-wedges  must  be  moved  to  an  extent  suffi- 
cient to  overcome  this  rotation  in  order  to  retore  the  stan- 
dard field.  The  effect  is  dependent  upon  the  fact  that  by  this 
movement  the  thickness  of  the  quartz  is  increased  or  dimin- 
ished until  it  compensates  for  the  rotation  produced  by  the 
solution.  The  extent  of  movement  of  the  quartz  is  registered 
upon  a  linear  scale,  which  is  read  by  means  of  a  lens  and  ver- 


i6 


FOOD   ANALYSIS 


nier.  White  light  is  employed  in  making  the  observations. 
A  form  of  the  Laurent  instrument,  with  quartz-wedge  com- 
pensation, and  employing  white  light,  is  made.  An  instru- 
ment has  been  devised  in  which  the  field  is  divided  vertically 
into  three  zones,  the  central  one  being  a  broad  band.     Dupli- 


FlG.  12. 


cate  Nicol  prisms  are  so  arranged  that  the  lateral  zones  agree 
in  tint,  thus  making  stronger  contrast  with  the  central  zone. 
The  polarimeter  shown  in  figure  12  is  now.  the  standard 
instrument.  It  has  been  improved  lately  by  the  substitution 
of  a  heavy  iron  stand  for  the  rickety  tripod,  but  is  still  in- 
complete.    It  has  two  serious  defects.    The  illumination  of 


POLARIMETRY  1 7 

the  scale  is  awkward,  and  it  is  not  convenient  for  examina- 
tions at  temperatures  above  normal. 

The  illumination  of  the  scale  is  done  by  a  mirror  over  the 
eye-lens  which  receives  light  from  the  main  lamp.  This  in- 
terferes with  the  eye  reaching  its  highest  sensitiveness.  In 
the  laboratory  of  one  of  us  (L)  the  following  arrangement 
has  been  adopted.  The  polarimeter  is  in  the  balance-room, 
close  to  a  small  opening  in  the  board  partition,  on  the  other 
side  of  which  is  the  source  of  light.  In  daylight  work  the 
scale  can  be  read  without  special  light,  but  if  greater  sensitive- 
ness of  the  eye  is  needed  a  focussing  cloth  is  thrown  over  the 
instrument  and  operator,  and  the  scale  is  illuminated  by  a 
small    incandescent    lamp. 


FJ 


operated  by  two  dry  cells. 
The   lamp  is  inserted  just 
under  the  mirror  that  re-      r- 
flects  the  scale  and  is  con-      I 
trolled   by   a   make-circuit      \_ 
key  as  usual. 

For  examinations  at  tem-       5 
peratures     above     normal,       i- 
Leach    employs    a    double  Fig.  13. 

metal  tube,  similar  to  the 

ordinary  condenser,  the  inner  channel  being  heavily  gilded  to 
prevent  corrosion  by  acid  liquids.  Arrangements  must  be  made 
for  taking  temperatures  during  observation  and  for  expansion 
and  contraction  of  the  liquid  in  the  inner  tube  when  this  is 
closed  by  the  glass  fronts.  For  taking  temperature,  it  is  usual  to 
provide  a  tube  at  the  center,  connecting  with  the  annulus,  in 
which  a  thermometer  is  inserted.  For  expansion,  Cochran  pro- 
vides a  short  tube  at  one  end,  communicating  with  the  inner  tube. 
Figure  13  is  a  sketch  of  a  form  designed  by  one  of  us  (L)  in 
which  the  expansion  and  temperature  tubes  are  combined.  It 
is  made  of  brass.  The  inner  tube  is  197  mm.  long.  This 
3 


1 8  FOOD  ANALYSIS 

allows  the  standard  length  of  200  mm.  to  be  obtained  by 
washers,  against  which  the  glass  circles  rest.  These  are  held 
in  place  by  caps,  which  screw  into  the  solid  end-pieces.  The 
inner  tube  and  the  surface  on  which  the  washers  rest  should 
be  well  gilded.  The  joints  need  not  be  brazed  as  the  tem- 
perature will  never  be  near  that  of  the  melting-point  of  soft 
solder.  At  each  end,  somewhat  above  the  middle  horizontal 
line  and  communicating  with  the  annulus,  is  a  short  tube  about 
0.7  cm.  in  diameter.  These  are  for  attachment  of  rubber 
tubes  carrying  water.  By  placing  them  above  the  middle 
Hne,  the  tube  will  He  properly  in  the  trough  of  the  instrument. 
In  the  middle  is  a  tube  3  cm.  high,  of  the  same  diameter  as 
the  inner  tube  and  communicating  with  it.  It  must  be  in 
such  direction  as  to  be  upright  when  the  tube  is  in  position 
in  the  instrument.  This  tube  is  for  expansion  and  holds  the 
thermometer,  which  is  set  down  as  far  as  possible  without 
interfering  with  the  observation.  The  thermometer  should  be 
about  20  cm.  long,  with  a  scale  from  0°  to  100°.  It  is  easily 
fastened  by  slipping  a  short  piece  of  rubber  tube  over  it,  and 
over  the  brass  tube.  Holes  can  be  cut  in  a  focussing  cloth 
so  that  the  instrument  and  operator  can  be  in  darkness,  the 
scale  being  read  by  means  of  the  electric  lamp  as  noted  above. 

A  metal  vessel  holding  several  liters  is  provided  with  heating 
arrangements,  a  rubber  tube  leads  from  it  to  one  of  the  water- 
tubes,  and  an  exit  is  provided  through  the  other.  The  water 
in  the  vessel  is  allowed  to  flow  through  the  observation  tube 
at  such  a  rate  as  will  maintain  the  proper  temperature  in  it. 

As  many  of  these  examinations  are  for  differential  temper- 
ature readings,  it  will  often  be  unnecessary  to  connect  up  the 
hot- water  apparatus.  The  observation  tube  should  be  closed 
with  corks,  the  annulus  filled  with  hot  water,  all  its  openings 
similarly  closed,  and  then  placed  in  water  at  a  suitable  tempera- 
ture for  at  least  five  minutes.  It  is  removed,  wiped  dry,  the 
glass  fronts  fastened  in  the  usual  way,  and  the  liquid  to  be 


POLARIMETRY  I9 

examined  run  in  through  the  thermometer  opening.  It  will  be 
easy  to  do  this  without  retaining  air-bubbles.  The  thermometer 
is  fastened  by  the  short  rubber  tube,  allowed  a  few  minutes  to 
reach  the  temperature  of  the  inner  liquid,  the  apparatus  placed 
in  the  polarimeter  and  the  reading  quickly  taken.  It  may  be 
wrapped  in  some  non-conducting  material  while  waiting  for  the 
thermometer  to  reach  its  highest  point.  Observation  with  hot 
tubes  should  be  made  quickly ;  if  a  number  are  to  be  made,  an 
interval  of  a  few  minutes  should  be  allowed  to  intervene 
between  each,  during  which  the  polarimeter  trough  should  be 
opened.  The  dehcate  optical  train  may  be  injured  by  much 
heating. 

Sources  oj  Light. — For  white  light,  oil,  gas,  or  electric  lamps 
are  employed,  of  which  numerous  patterns  are  furnished.  Sat- 
isfactory results  may  be  obtained  by  the  Welsbach  lamp. 
Wiley  recommends  the  use  of  the  acetylene  flame,  especially 
for  deeply  colored  solutions. 

For  monochromatic  light,  the  lamp  usually  employed  is 
a  Bunsen  burner  with  a  ledge  at  the  top  for  holding  some 
solid. sodium  compound.  A  fused  mixture  of  sodium  chlorid 
and  phosphate  is  better  than  sodium  chlorid  alone.  The  fol- 
lowing is  an  excellent  method  for  obtaining  a  steady,  strong, 
yellow  light:  Strips  of  common  filter-paper  5  cm.  wide  and 
about  50  cm.  long  are  soaked  in  a  strong  solution  of  sodium 
chlorid  and  thiosulfate,  dried,  and  rolled  into  a  hollow  cylin- 
der of  such  size  as  to  fit  firmly  on  the  top  of  the  Bunsen 
burner.  The  cylinder  is  kept  from  unrolling  by  a  few  turns 
of  fine  iron  wire.  The  flame  bums  at  the  top  of  the  cylinder, 
giving  for  the  first  few  minutes  a  luminous  cone,  but  soon 
becoming  pure  yellow.  The  cylinder  becomes  a  friable 
charred  mass,  but  if  not  disturbed  may  be  used  for  some  time 
continuously  or  at  intervals. 

Specific  Rotatory  Power. — The  specific  rotatory  power  of 
a  substance  is  the  amount  of  rotation,   in  angular  degrees, 


20  FOOD   ANALYSIS 

produced  by  a  solution  containing  one  gram  of  the  substance 
in  I  c.c.  examined  in  a  column  one  decimeter  long.  It  is 
usually  represented  by  the  symbol  [«].  To  indicate  the  light 
employed  in  the  observation,  [«]d  or  [a]j  is  used,  d  stands  for 
light  of  wave  length  corresponding  to  the  D  line  of  the  solar 
spectrum  (sodium  flame)  and  j  (jaune)  for  the  transition  tint. 
It  is  usual  also  to  indicate  in  the  same  symbol  the  temperature 
of  observation;    thus,  [aY°. 

Under  ordinary  methods  of  observation  the  specific  rota- 
tory power  is  represented  by  the  following  formula: 

W^  =  ^;  in  which 

[a]^  is  the  specific  rotatory  power  for  the  light  of  the  sodium  flame, 
a  is  the  angular  rotation  observed, 

c  is  the  concentration  expressed  in  grams  per  loo  c.c.  of  liquid, 
/  is  the  length  of  the  tube  in  decimeters. 

Comparison  oj  Scales  oj  Various  Instruments. — Polarimeters 
are  now  usually  provided  with  a  scale  reading  to  loo  when 
a  certain  quantity  of  sucrose,  called  the  normal  weight,  is 
dissolved  in  water  and  made  up  to  loo  c.c.  For  the  German 
instruments,  which  are  largely  used  in  the  United  States,  this 
is  26.048  grams.  This  scale  is  known  as  "  Ventzke,"  "Schmidt 
and  Hansch,"  and  "sugar"  scale. 

The  instruments  made  by  Schmidt  and  Hansch  are  gradu- 
ated to  read  correct  percentages  when  the  normal  weight  of 
sugar  is  contained  in  100  Mohr's  cubic  centimeters  and  ob- 
served in  a  2  decimeters  tube  at  17.5°.  With  the  Laurent 
apparatus  the  normal  weight  of  the  sugar  should  be  contained 
in  100  true  cubic  centimeters. 

The  volume  of  100  Mohr's  cubic  centimeters  .  is  that  of 
100  grams  of  water  at  17.5°  weighed  in  air  with  brass  weights; 
it  is  equal  to  100.234  true  cubic  centimeters.  For  the  nor- 
mal weight  of  26.048  grams  in  100  Mohr's  cubic  centimeters 


SPECTROSCOPY  21 

of  solution,  may  be  substituted  25.9872  grams  in  100  true 
cubic  centimeters  at  17.5°. 

At  the  session  of  the  International  Commission  for  Uniform 
Methods  of  Sugar  Analysis  held  at  Paris,  July  24,  1900,  it 
was  agreed  that  the  normal  weight  shall  be  fixed  at  26  grams 
in  100  true  c.c.  at  20°,  weighed  in  air  with  brass  weights  (see 
under  "Sucrose"). 

The  following  factors  may  be  employed  for  the  conversion 
of  data  obtained  by  different  instruments: 

I  division  Schmidt  and  Hansch  0,3468°  angular  rotation  D. 

1°  angular  rotation  D  2 .8835  divisions  Schmidt  and  Hansch. 

1°  angular  rotation  D  0.75 1 1  division  Wild. 

I  division  Laurent  0.2167°  angular  rotation  D. 

1°  angular  rotation  D  4-6154  divisions  Laurent. 

Correction  jor  Precipitate.— In  some  cases  the  volume  of 
precipitate  produced  by  the  clarifying  agents  is  considerable, 
and  a  correction  would  be  necessary.  The  error  may  be 
eliminated  by  Scheibler's  method:  A  normal  weight  of  the 
sample  is  dissolved  in  water  or  proper  solvent,  treated  with 
the  clarifying  agent,  the  liquid  made  up  to  100  c.c,  shaken 
well,  filtered,  and  a  reading  taken  of  the  filtrate.  A  second 
portion  of  normal  weight  is  treated  in  the  same  way  except  that 
it  is  made  up  to  200  c.c.  before  filtration.  Great  care  must 
be  taken  in  the  readings.  The  true  reading  is  obtained  by 
dividing  the  product  of  the  two  readings  by  their  difference. 

Spectroscopy. 

In  practical  analysis  the  spectroscope  is  mostly  useful  in 
detecting  some  of  the  rarer  elements  in  ashes  and  water-resi- 
dues. For  this  purpose  the  direct  vision  instrument  shown 
in  figure  14  is  sufficient.  It  will  often  serve  for  the  examina- 
tion of  absorption  bands,  but  for  precise  research  in  distinguish- 
ing colors  and  specific  absorptions  a  more  elaborate  instru- 
ment, as  shown  in  figure  15,  will  be  needed.    Zeiss  makes  a 


22 


FOOD  ANALYSIS 


direct  vision  instrument  in  which  the  Hght  enters  by  openings 

placed  side  by  side,  but  forms 
spectra  that  are  exactly  super- 
posed. By  this  means  a  solution 
of  known  composition  can  be  ex- 
amined in  comparison  with  a 
material  to  be  tested;  or  two 
flame-tests  may  be  compared. 
This  instrument  can  be  mounted 
as  shown  in  figure  14. 

For  the  examination  of  ashes 
or  water-residues,  the  material  is 
mixed  with  a  few  drops  of  hydro- 
chloric acid,  a  portion  of  the  mass 
taken  up  on  a  loop  of  clean  plati- 
num wire  and  held  in  a  non-lumin- 
ous flame,  the  spectrum  being  ex- 
amined through  the  instrument.  It 
is  important  that  the  first  effects 
should  be  noted,  as  some  sub- 
stances   volatilize    quickly.      The 


Fig.  14. 


platinum  wire  should  be  cleaned  by  dipping  it  in  a  little  pure 


Fig.  15. 


MICROSCOPY  23 

hydrochloric  acid  and  heating  it  in  the  gas  flame  until  it  im- 
parts no  color  thereto. 

For  the  observation  of  absorption-bands  of  liquids,  small 
flat  bottles  with  ground  and  polished  sides  are  used.  These 
permit  the  observation  of  a  thin  or  thick  stratum  as  desired. 
Deeply  colored  solutions  should  not  be  used  since  large  por- 
tions of  the  spectrum  may  be  cut  out  by  general  absorption 
and  the  distinctive  selective  absorption  be  lost. 

For  some  purposes  the  microspectroscope  will  be  needed, 
but  its  use  is  practically  limited  to  medico-legal  work. 

Fluorescence. 

This  may  be  detected  satisfactorily  in  the  manner  described 
by  Allen:  A  test-tube  or  cylindrical  beaker  is  nearly  filled 
with  a  perfectly  clear  solution  of  the  substance,  set  upon  a 
dark  surface,  and  observed  from  above.  Another  plan  is  to 
make  a  streak  of  the  liquid  on  a  piece  of  black  glass  or  pol- 
ished black  marble  and  examine  this  in  a  good  white  light. 
Tests  can  also  be  made  by  directing  a  ray  of  white  light  from 
any  source  through  the  side  of  a  beaker  containing  the  liquid 
and  looking  at  it  from  above.  In  all  the  methods  the  liquid 
must  be  perfectly  clear  or  misleading  reflection-effects  are  pro- 
duced. 

Microscopy. 

For  preliminary  examination  of  food  samples  a  hand  lens 
is  useful,  but  the  practical  analysis  involves  the  use  of  the 
compound  microscope.  A  good  instrument  can  now  be  ob- 
tained at  comparatively  small  cost.  It  should  be  supplied 
with  at  least  two  objectives,  one  of  low  power,  about  16  mm. 
focus  (§  in.),  and  one  of  rather  high  power,  4  mm.  focus 
(J  in.).  The  usefulness  of  a  microscope  is  much  enhanced  by 
the  attachment  of  a  sub-stage  achromatic  condenser  and  ad- 
justable diaphragm.  Polarizing  apparatus,  including  a  selenite 
plate,  is  needed,  especially  for  differentiation  of  starches. 


24 


FOOD  ANALYSIS 


The  instrument  shown  in  figure  i6,  of  American  construc- 
tion, is  arranged  to  receive  all  accessories.  A  double  nose- 
piece  will  be  sufficient,  as  the  high-power  lens  which  is  shown 


Fig.  I 6. 


is  not  needed  for  chemical  work.     The  outfit,  with  two  lenses 
and  polarizing  attachment  with  selenite,  costs  about  $70. 

For  the  better  differentiation  of  objects  submitted  to  ex- 
amination under  the  microscope,  clearing  and  staining  agents 
are  used.     In  many  cases  details  of  structure  are  brought  out 


MICROSCOPY  25 

sharply  by  using  a  dense  liquid  as  a  mounting  fluid.     The 
following  is  a  list  of  the  important  apparatus  and  reagents: 

Slides  and  cover- glasses. 

Agate  mortar^  2.5  cm.  outside  diameter,  and  a  somewhat 
larger  glass  triturating  mortar  are  useful  for  preparing  mate- 
rials. The  pestles  of  agate  mortars  are  usually  inconveniently 
short,  and  are  much  improved  by  being  mounted  in  a  wooden 
handle. 

Dissecting  needles  are  easily  made  by  sawing  off  the  metal 
portion  of  an  ordinary  penholder  close  to  the  wood  and  for- 
cing the  eye-end  of  a  sewing  needle  under  the  ferrule  which  has 
been  thus  formed.  A  neat  form  of  a  needle-holder  is  furnished 
by  the  instrument  makers. 

Small  forceps  and  sharp  scissors  will  be  needed. 

Watch-glasses  are  used  for  immersing  specimens  in  liquids; 
still  better  are  the  so-called  Syracuse  glasses,  the  best  form 
of  which  has  a  ground-glass  surface  for  memoranda. 

Water.  Distilled  water  is  best,  but  any  clear,  colorless 
water  not  containing  much  mineral  or  organic  matter  will 
answer. 

Glycerol.    A  pure  article  is  easily  obtained. 

Alcohol.  The  commercial  95  per  cent,  form  is  used  for 
hardening  tissues,  but  for  ordinary  microscopic  work,  a  70 
per  cent,  solution  will  suffice. 

Methyl  alcohol  in  the  purified  form  now  obtainable  may  be 
substituted  in  many  instances  for  common  alcohol. 

Ether^  chlorojorm,  benzene,  and  carbon  disulfid  are  occasion- 
ally used  for  their  solvent  action,  especially  to  remove  oils, 
waxes,  and  resins.  Carbon  tetrachlorid  will  be  also  of  use. 
For  these  extractions  it  will  often  be  most  satisfactory  to  ope- 
rate in  a  small  continuous  extraction  apparatus,  with  repeated 
washings,  as  described  under  ''Extraction,"  drying  the  material 
at  a  gentle  heat  to  remove  all  the  solvent,  which  would  inter- 
fere with  the  action  of  watery  solutions  or  glycerol. 
4 


26 


FOOD   ANALYSIS 


Chloral   hydrate   solution^ — a   saturated  solution   in   water. 
Chloral  hydrate  and  iodin  solution, — a  portion  of  the  above 
solution  to  which  a  trace  of  iodin  has  been  added. 

Potassium  iodid  and  iodin  solution, — potas- 
sium iodid,  0.4  gram;  iodin,  o.i  gram;  water, 
20  c.c. 

Zinc  chloriodid  and  iodin  solution:  Dissolve  5 
grams  of  zinc  chlorid  and  1.6  grams  of  potassium 
iodid  in  17  c.c.  of  water  and  saturate  with  iodin. 

Sodium  hydroxid, — 5  per  cent,  solution.  In 
some  instances  a  strong  solution  is  employed, 
which  is  best  prepared  when  required. 

Acid    phloroglucol.      This    is    best    prepared 
when  needed  by  dissolving  a  few  milligrams  of 
phloroglucol  in    i    c.c.   of   alcohol  and    adding 
a  drop  of  hydrochloric  acid. 

Bottles  (figure  17)  with  caps  ground  on  and  pipet,  are  the 
best  for  reagents.  A  little  vaselin  may  be  put  on  the  joint  to 
prevent  sticking. 


Fig.  17. 


WATER  AND  FIXED  SOLIDS  27 

CHEMICAL  DATA 
Water  and  Fixed  Solids  (Extract). 

Water  is  usually  determined  with  sufficient  accuracy,  pro- 
vided other  volatile  bodies  are  not  present,  by  heating  the 
material  (solids  should  be  finely  divided)  in  a  flat  dish  on  the 
water-bath  or  in  the  water-oven  until  it  ceases  to  lose  weight. 
The  residue  constitutes  the  fixed  solids  or  extract.  Flat 
platinum  dishes  from  4  to  8  cm.  in  diameter  and  0.5  cm.  high 
are  well  adapted  to  this  work.  They  should  rest  on  porcelain  or 
asbestos  rings.  Nickel  dishes  are  often  applicable,  especially 
the  broad  shallow  crucible  covers  made  in  dish  form.  Dishes 
of  glass — especially  the  shallow  (Petri)  dishes  used  for  microbe 
culture — and  porcelain  are  suitable;  aluminum  and  tin  less 
so.  In  many  cases  drying  will  be  facilitated  by  using  an 
absorbent  material  such  as  pure  quartz  sand,  powdered  asbestos, 
or  pumice-stone.  These  materials  should  be  extracted  with 
dilute  hydrochloric  acid,  well  washed,  and  well  dried  before  use. 
The  quantity  used  should  be  rapidly  weighed,  preferably  in  the 
dish  in  which  the  operation  is  to  be  carried  out.  It  is  advisable 
to  cover  the  dish  with  a  nearly  flat,  thin  watch-glass  in  all  the 
weighings.  By  a  few  trials  a  glass  can  be  selected  which  fits 
fairly  close  to  the  rim  of  the  dish  and  restricts  evaporation  or 
absorption  of  water.  It  is  often  convenient  to  weigh  a  small 
stirring-rod  with  the  dish  and  absorbent. 

In  many  cases  liquid  can  be  measured  directly  into  the 
dish,  the  residue  being  recorded  in  grams  per  100  c.c.  or  other 
suitable  ratio. 

Sirupy  and  gelatinous  liquids  or  those  containing  much  solid 
matter,  especially  if  this  be  somewhat  difficult  to  dry,  may 
often  be  more  satisfactorily  treated  by  diluting  a  weighed 
portion  with  several  times  its  weight  of  water,  evaporating  a 
measured  or  weighed  amount  of  the  dilute  liquid,  and  calcu- 
lating the  amount  of  residue  in  the  original  substance. 


28 


FOOD  ANALYSIS 


The  ordinary  water-bath  and  water-oven  need  no  descrip- 
tion. The  temperature  of  materials  heated  on  the  former  is 
usually  much  less  than  ioo°;  in  the  latter,  slightly  below 
ioo°.  By  using  strong  brine  a  somewhat  higher  temperature 
may  be  obtained.     In  the  case  of  very  hygroscopic  or  easily 


Fig.  1 8. 


decomposable  bodies  it  may  be  necessary  to  dry  in  a  current 
of  hydrogen  or  at  reduced  pressure. 

Figure  i8  shows  a  drying  oven  for  use  with  a  current  of 
hydrogen.  The  apparatus  was  designed  by  Caldwell  for 
determining  moisture,  ether-extract,  and  crude  fiber  as  pre- 
scribed by  the  A.  O.  A.  C,  the  three  data  being  determined 
on  the  same  sample. 


WATER  AND  FIXED  SOLIDS  ^9 

The  bath  is  made  of  copper  and  is  24  cm.  long,  15  high, 
and  8.5  broad.  It  stands  in  a  piece  of  sheet-copper  bent  at 
right  angles  along  the  sides,  as  shown  in  the  end  view;  on 
one  side  this  vertical  part  need  not  be  over  i  cm.  high,  just 
enough  to  project  a  little  up  the  side  of  the  bath,  which  rests 
snugly  against  it;  along  the  other  side  it  projects  upward,  at 
a  little  distance  from  the  side  of  the  bath,  about  15  mm.,  and 
to  about  the  height  of  4  cm.;  opposite  each  of  the  tubes  of 
the  bath  a  slot  is  cut  in  this  vertical  part,  which  serves  then  as 
a  shoulder  against  which  the  glass  tube  rests  when  in  place,  to 
keep  it  from  slipping  down  and  out  of  position. 

The  tube  for  containing  the  substance  has  at  the  zone  a 
three  small  projections  on  the  inner  surface,  which  support 
a  perforated  platinum  disk  of  rather  heavy  platinum  foil  carry- 
ing the  asbestos  filter.  This  tube  is  13  cm.  long  and  23  mm. 
inner  diameter,  and  weighs,  with  its  closed  stoppers,  about 
30  grams. 

The  filter  is  readily  made  in  the  same  manner  as  the  Gooch 
filter,  the  tube  being  first  fitted  to  a  suction  flask  by  an  en- 
largement of  one  of  the  holes  of  the  rubber  cork,  or,  better 
still,  by  shpping  a  short  piece  of  rubber  tube  over  it,  of  such 
thickness  that  it  will  fit  tightly  in  the  mouth  of  a  suction  flask 
provided  with  lateral  tube  for  connection  with  the  suction.  A 
thin  welt  of  asbestos  is  sufficient;  if  it  is  too  thick,  the  gas 
and  ether  will  not  flow  through  readily. 

About  2  grams  of  the  substance  are  put  in  this  tube,  pre- 
viously weighed  with  the  stoppers  h  and  c,  and  the  weight  of 
the  substance  accurately  determined  by  weighing  tube  and 
contents.  The  stoppers  are  removed,  a  band  of  thin  asbestos 
paper  is  wound  around  the  end  d  of  the  tube,  a  little  behind 
the  slight  shoulder  at  the  rim,  as  many  times  as  may  be  neces- 
sary to  make  a  snug  fit,  when  this  tube  is  slid  down  into  the 
copper  tube  in  the  bath,  thus  preventing  circulation  of  air 
between  the  glass  and  the  copper  tubes  that  would  retard  the 


30  FOOD  ANALYSIS 

heating  of  the  former;  the  stopper  e  is  put  in  the  lower  end 
of  the  tube  for  connection  with  the  hydrogen  supply,  and  the 
stopper  /  in  the  upper  end;  this  latter  stopper  is  connected 
by  rubber  tube  with  a  glass  tube  slipping  easily  through  one 
of  the  holes  of  a  rubber  cork  closing  a  small  flask  containing 
a  little  sulfuric  acid,  into  which  this  tube  just  dips;  when  as 
many  tubes  as  are  to  be  charged  are  thus  arranged  in  place  and 
the  hydrogen  is  turned  on,  the  even  flow  of  the  current  through 
the  whole  number  is  secured  by  raising  or  lowering  a  very  little 
the  several  tubes  through  which  the  outflow  passes,  so  as  to  get 
a  little  more  back  pressure  for  one,  or  a  little  less  for  another, 
as  may  be  found  necessary.  When  the  drying  is  supposed  to  be 
completed,  the  tubes  are  weighed  again  with  their  closed 
stoppers,  and  so  on. 

For  ether-extraction  the  unstoppered  tube  with  contents  is 
put  directly  into  the  extractor. 

Carr  and  Osborne  have  made  an  extended  series  of  inves- 
tigations as  to  the  determination  of  water,  and  find  that  more 
accurate  results  may  be  obtained  if  the  operation  be  conducted 
under  a  diminished  pressure  at  a  temperature  not  exceeding 
70°  C.  Under  these  conditions  it  was  found  possible  to  dehy- 
drate levulose  completely,  without  decomposition.  The  oven 
is  made  of  a  section  of  metal  tubing,  from  15  to  20  cm.  in 
diameter  and  30  to  40  cm.  long.  One  end  is  closed  air-tight 
by  a  brass  end-piece,  brazed  or  attached  by  a  screw.  The 
other  end  is  detachable  and  is  made  air-tight  by  ground  surfaces 
and  a  soft  washer.  On  the  top  are  apertures  for  the  insertion  of 
a  vacuum-gauge  and  for  attachment  to  a  vacuum-apparatus, 
thermostat  and  thermometer.  The  aperture  for  admission  of 
air  or  hydrogen  is  best  placed  at  the  fixed  end.  The  oven  may 
be  heated  by  a  single  burner,  but  a  series  of  small  jets  is  prefer- 
able. The  metal  should  be  protected  by  sheet  asbestos.  The 
temperature  of  the  oven  can  be  kept  uniform  by  a  gas  regulator, 
or  by  attention  to  the  lamp. 


WATER  AND   FIXED   SOLIDS  3 1 

The  method  of  operating  is  as  follows:  Clean  pumice-stone 
of  two  grades  of  fineness  is  used,  one  that  just  passes  through 
a  I  mm.  mesh  and  one  that  passes  through  a  6  mm.  mesh. 
These  are  digested  with  hot  2  per  cent,  sulfuric  acid,  washed 
by  decantation  until  the  wash-water  is  free  from  acid,  placed, 
wet,  in  a  sand  crucible  and  heated  to  redness.  When  the 
water  is  expelled,  the  material  may  either  be  placed  hot  into  a 
desiccator  or  directly  into  the  drying  dishes.  In  loading  the 
dishes,  place  a  thin  layer  of  dust  over  the  bottom  of  the  dish 
to  prevent  the  material  to  be  dried  from  coming  in  contact 
with  the  metal;  over  this  layer  place  the  larger  particles,  nearly 
filling  the  dish.  If  the  stone  has  been  well  washed,  no  harm 
may  result  from  placing  the  dish  and  stone  over  the  flame  for  a 
moment  before  transferring  to  the  desiccator  preparatory  to 
weighing. 

If  the  material  to  be  dried  is  dense,  it  is  diluted  until  the 
specific  gravity  is  in  the  neighborhood  of  1.08  by  dissolving  a 
weighed  quantity  in  a  weighed  quantity  of  water.  (Alcohol 
may  be  substituted  in  material  not  precipitable  thereby.)  Of 
this,'  2  to  3  grams  may  be  distributed  over  the  stone  in  a  dish 
the  area  of  which  is  in  the  neighborhood  of  20  sq.  cm.,  or  one 
gram  for  each  7  sq.  cm.  of  area.  The  material  is  distributed 
uniformly  over  the  pumice  by  means  of  a  pipet  weighing- 
bottle  (weighing  direct  upon  pumice  will  not  answer),  ascer- 
taining the  weight  taken  by  difference. 

The  dishes  are  placed  in  the  vacuum-oven,  which  should  be 
maintained  at  a  pressure  of  not  more  than  125  mm.  of  mer- 
cury. The  temperature  must  not  exceed  about  70°.  All 
weighings  must  be  taken  with  the  dish  covered  by  a  close-fitting 
plate.  The  open  dish  must  not  be  exposed  to  the  air  longer 
than  absolutely  necessary.  Weighings  may  be  made  at  inter- 
vals of  two  or  three  hours. 

In  the  laboratory  of  the  United  States  Geological  Survey  a 
sheet-iron  or  nickel  basin  about  10  cm.  in  diameter  and  3 


32  FOOD   ANALYSIS 

cm.  deep  is  set  upon  an  iron  plate  which  is  heated  directly  by 
the  burner.  A  platinum  or  pipe-clay  triangle  rests  in  the 
basin  and  supports  the  dish  containing  the  Hquid  to  be  evap- 
orated. It  is  stated  that  almost  any  liquid  can  be  evaporated 
in  this  way  without  sputtering.  The  temperature,  however,  is 
liable  to  be  too  high  for  many  organic  bodies. 

Parsons  has  obtained  good  results  in  the  drying  of  sensitive 
organic  substances  by  the  following  method:  A  perfectly 
neutral  petroleum  oil,  free  from  animal  or  vegetable  oils  and 
mineral  substances,  sp.  gr.  0.920,  flash  test  224°,  fire  test  260°, 
boiHng-point  about  288°,  is  heated  to  about  1 20°  for  some  time 
and  preserved  in  a  well-stoppered  vessel.  A  quantity  of  oil 
about  six  times  that  of  the  weight  of  the  substance  to  be  dried 
is  heated  in  an  evaporating  dish  in  a  drying  oven  to  a  tempera- 
ture of  1 1 5°,  and  then  weighed.  The  weighed  portion  of  the  sub- 
stance is  put  into  the  oil;  if  it  be  very  moist,  it  is  added  in  small 
portions.  Slight  effervescence  will  usually  occur,  and  the  mass 
should  be  kept  in  the  drying  oven  for  a  short  time  after  effer- 
vescence has  ceased.  The  evaporating  dish  containing  the  oil 
and  substance  is  weighed;  the  loss  is  moisture.  The  whole 
operation  may  be  completed  in  less  than  half  an  hour. 


Nitrogen. 

Total  Nitrogen. — The  Kjeldahl- Gunning  method  is  the 
most  satisfactory. 

The  reagents  and  operation  are  as  follows : 

Potassium  Sulfate.  A  coarsely  powdered  form  free  from 
nitrates  and  chlorids  should  be  selected. 

Suljuric  Acid.  This  should  have  a  sp.  gr.  1.84  and  be  free 
from  nitrates  and  ammonium. 

Standard  Acid.  -^  Sulfuric  or  hydrochloric  acid,  the  strength 
of  which  has  been  accurately  determined. 

Standard  A  Ikali.     -^  Ammonium  hydroxid,  sodium  hydroxid. 


NITROGEN  33 

or  barium  hydroxid,  the  strength  of  which  in  relation  to  the 
standard  acid  must  be  accurately  determined. 

Strong  Sodium  Hydroxid  Solution.  500  grams  should  be 
added  to  500  c.c.  of  water,  the  mixture  allowed  to  stand  until 
the  undissolved  matter  settles,  the  clear  liquor  decanted  and 
kept  in  a  stoppered  bottle.  It  will  be  an  advantage  to  de- 
termine approximately  the  quantity  of  this  solution  required 
to  neutralize  20  c.c.  of  the  strong  sulfuric  acid. 

Indicator.  Cochineal  solution  is  recommended  by  the  A. 
O.  A.  C,  but  methyl-orange  and  azolitmin  are  satisfactory. 
Phenolphthalein  is  not  well  adapted  to  titration  of  ammonium 
compounds.     (See  under  ''Indicators.") 

Digestion  Flasks.  Pear-shaped  round-bottomed  flasks  of 
hard,  moderately  thick,  well-annealed  glass,  about  22  cm. 
long,  maximum  diameter  of  6  cm.,  tapering  gradually  to  a 
long  neck,  2  cm.  in  diameter  at  the  narrowest  part,  and  shghtly 
flared  at  the  mouth. 

Distillation  Flasks.  Jena-glass  flasks  of  about  550  c.c.  ca- 
pacity. A  copper  flask,  such  as  sometimes  used  in  the  manu- 
facture of  oxygen,  may  be  substituted. 

Combined  Digestion  and  Distillation  Flasks.  Jena-glass 
round-bottomed  flasks  with  a  bulb  12.5  cm.  long  and  9  cm.  in 
diameter,  the  neck  cylindrical,  15  cm.  long  and  3  cm.  in  di- 
ameter, flared  slightly  at  the  mouth. 

Process.  0.7  to  3.5  grams,  according  to  the  proportion  of 
nitrogen,  are  placed  in  a  digestion  flask.  Then  10  grams  of 
powdered  potassium  sulfate  and  15  to  25  c.c.  (ordinarily  about 
20  c.c.)  of  the  strong  sulfuric  acid  are  added  and  the  digestion 
conducted  as  follows:  The  flask  is  placed  in  an  inclined  posi- 
tion and  heated  below  the  boiling-point  of  the  acid  for  from  five 
to  fifteen  minutes,  or  until  frothing  has  ceased.  Excessive 
frothing  may  be  prevented  by  the  addition  of  a  small  piece  of 
paraffin.  The  heat  is  raised  until  the  acid  boils  briskly.  A 
small,   short-stemmed  funnel  may  be  placed  in  the  mouth 


34 


FOOD  ANALYSIS 


of  the  flask  to  restrict  the  circulation  of  air.  No  further  atten- 
tion is  required  until  the  liquid  has  become  clear  and  colorless, 
or  not  deeper  than  a  pale  straw. 

When  Kjeldahl  operations  are  carried  out  in  limited  number, 
the  arrangement  used  in  the  laboratory  of  one  of  us  (L)  has  been 
found  very  satisfactory.  A  double-Y,  terra  cotta  drain-pipe, 
about  20  centimeters  internal  diameter,  is  connected  by  an  elbow 
directly  with  the  chimney-stack.  The  digestion  flasks  are 
supported  as  shown  in  the  rough  sketch,  figure  20  (not  drawn 
exactly  to  scale).     Two  flasks  can  be  operated  at  once.     The 


Fig.  19. 


Fig. 


central  opening  is  convenient  for  other  operations  producing 
fumes.  Openings  not  in  use  are  closed  by  circles  of  heavy 
asbestos. 

The  apparatus  shown  in  figure  19  is  used  when  many  de- 
terminations are  made.  As  corrosive  vapors  are  given  off, 
it  must  be  placed  under  a  hood.  The  central  opening  in 
the  ventilating  pipe  shown  in  figure  20  will  be  satisfactory;  the 
mouths  of  the  flasks  should  be  well  inside  the  margin  of  the  pipe. 

When  the  liquid  has  become  colorless  or  very  light  straw 


NITROGEN  35 

yellow,  it  is  allowed  to  cool,  diluted  with  icx)  c.c.  of  water  if  the 
smaller  form  of  flask  has  been  used,  the  liquid  transferred  to  the 
distilling  flask,  and  the  digestion  flask  rinsed  with  two  portions 
of  water,  50  c.c.  each,  which  are  also  transferred  to  the  distilling 
flask.  With  the  larger  form  of  flask  the  dilution  is  made  at  once 
by  the  cautious  addition  of  200  c.c.  of  water.  Granulated  zinc, 
pumice  stone,  or  0.5  gram  of  zinc  dust  is  added.  50  c.c.  of  the 
strong  sodium  hydroxid  solution,  or  sufficient  to  make  the 
reaction  strongly  alkaline,  should  be  slowly  poured  down  the  side 
of  the  flask  so  as  not  to  mix  at  once  with  the  acid  solution. 
It  is  convenient  to  add  to  the  acid  liquid  a  few  drops  of  phenol- 
phthalein  or  azolitmin  solution,  to  indicate  when  the  hquid  is 
alkaline,  but  it  must  be  noted  that  strong  alkaline  solutions 
destroy  the  former  indicator.  The  flask  is  shaken  so  as  to 
mix  the  alkaline  and  acid  liquids  and  at  once  attached  to  the 
condensing  apparatus.  The  receiving  flask  should  have  been 
previously  charged  with  a  carefully  measured  volume  of  the 
-^  acid  (100  c.c.  is  a  convenient  amount).  The  distillation  is 
conducted  until  about  150  c.c.  have  passed  over.  The  acid  is 
then  titrated  with  standard  alkali  and  methyl  orange,  cochineal, 
or  azolitmin,  and  the  amount  neutrahzed  by  the  distilled  am- 
monium hydroxid  determined  by  subtraction.  Each  c.c.  of  -7- 
acid  neutrahzed  is  equivalent  to  0.007  nitrogen. 

The  distillation  in  this  operation  requires  care,  as  the  amount 
of  ammonium  hydroxid  is  determined  by  its  neutrahzing  power, 
hence  solution  of  the  alkali  of  the  glass  will  introduce  error. 
Common  glass  is  not  satisfactory.  Block-tin  is  the  best 
material  for  the  Kjeldahl- Gunning  form,  but  Moerrs  has  shown 
that  it  is  not  adapted  to  the  methods  in  which  mercury  oxid 
is  employed.  He  found  that  Jena-glass  tubes  resist  the  action  of 
the  ammonium  hydroxid. 

The  most  satisfactory  condensing  arrangement  for  general 
laboratory  use  is  a  copper  tank  of  good  size,  through  which 


36 


FOOD  ANALYSIS 


several  condensing  tubes  pass.  Such  an  arrangement  is  shown 
in  side-view  in  figure  26.  A  more  detailed  view  of  the  con- 
struction as  applied  to  Kjeldahl  distillations  is  shown  in  figure 
21,  which  is  a  rough  sketch,  not  drawn  to  scale.  The  flask  is  the 
standard  Jena-glass  distilling  flask,  about  12  cm.  diameter,  the 
tank  should  be  high  enough  to  allow  of  a  condensing  tube  60 
cm.  long.  The  connection  of  this  with  the  receiving  flask  is 
made  by  means  of  a  bulb  tube  to  allow  for  occasional  drawing- 
back  of  the  liquid.  The  cork 
through  which  this  tube  passes 
into  the  flask  must  not  fit  closely, 
as  opportunity  must  be  given  for 
expansion  of  the  air.  The  safety 
tube  connecting  the  distilling 
flask  with  the  condenser  should 
terminate  a  httle  below  the  water 
level  in  the  tank.  The  apparatus 
may  be  satisfactorily  heated  by 
the  low  temperature  burner,  as 
shown  in  figure  31.  To  avoid 
spurting  of  the  boiling  liquid,  it 
is  usual  to  interpose  a  safety-tube 
between  the  distilling  flask  and 
the  condenser.  Many  forms 
have  been  suggested.  Those 
shown  in  figures  22  and  23  are  most  in  use.  Figure  23  is  the 
more  complex,  but  is  satisfactory.  The  distillation  will  be 
hastened  if  this  tube  be  covered  with  non-conducting  material. 
In  some  determinations  (as  in  pepper)  the  Kjeldahl- Gunning 
method  must  be  replaced  by  Arnold's  modification:  i  gram  of 
the  sample  is  mixed  with  i  gram  of  crystallized  copper  sulfate 
and  I  gram  of  mercuric  oxid.  The  potassium  sulfate- sulfuric 
acid  mixture  as  given  above  is  added  and  the  mass  heated 
cautiously  until  frothing  ceases,  when  the  temperature  is  raised 


Fig.  21. 


NITROGEN 


37 


and  the  digestion  completed.  The  liquid  is  diluted  for  dis- 
tillation, 50  c.c.  of  a  solution  of  commercial  potassium  sulfid 
(40  grams  to  1000  c.c.)  are  added,  and  sufficient  sodium  hy- 
droxid  as  usual.     The  liquid  is  liable  to  bump. 

Modification  jor  Nitrates.  If  nitrates  are  present  in  the 
material,  the  weighed  sample  is  well  mixed  with  35  c.c.  of 
sulfuric  acid  containing  2  per  cent.,  by  weight,  of  salicyHc  acid, 
and  the  mass  shaken  frequently  during  ten  minutes ;  5  grams  of 
sodium  thiosulfate  are  added  and  10  grams  of  potassium  sulfate. 


Fig.  22. 


Fig.  23. 


The  mixture  is  heated  very  gently  until  frothing  ceases  and  then 
according  to  the  usual  method.  The  nitrogen  in  the  distillate 
will  include  that  derived  from  the  nitrogen  of  the  nitrates. 

Albuminoid  Nitrogen. — Stutzer's  method  for  this  deter- 
mination requires  a  special  reagent: 

Copper  Hydroxid  Mixture.  100  grams  of  copper  sulfate 
are  dissolved  in  5000  c.c.  of  water,  25  c.c.  of  glycerol  added, 
and  then  a  dilute  solution  of  sodium  hydroxid  until  the  hquid 
is  alkaline.  The  mass  is  filtered,  the  precipitate  is  mixed  well 
with  water  containing  5  c.c.  of  glycerol  per  1000  c.c.  and 


38  FOOD   ANALYSIS 

washed  until  the  washings  are  no  longer  alkaline.  It  is  then 
rubbed  up  with  a  mixture  of  90  per  cent,  water  and  10  per 
cent,  glycerol  in  sufficient  quantity  to  obtain  a  uniform  magma 
that  can  be  measured  with  a  pipet.  The  quantity  of  copper 
hydroxid  per  c.c.  should  be  determined.  It  should  be  kept 
in  a  well-closed  bottle. 

Analytic  Method.  A  suitable  amount  of  the  material,  gen- 
erally about  0.7  gram,  is  heated  with  100  c.c.  of  water  to  100°, 
and  a  quantity  of  the  copper  hydroxid  mixture  containing 
about  0.5  gram  of  solid  added,  stirred  well,  allowed  to  cool, 
filtered,  washed  well  with  cold  water,  and  the  filter  and  pre- 
cipitate treated  by  the  Kjeldahl- Gunning  method. 

Substances  rich  in  starch  are  best  subjected  to  about  ten 
minutes'  warming  in  the  water-bath  instead  of  direct  boiling. 
With  substances  containing  much  phosphate  a  few  cubic 
centimeters  of  alum  solution  should  be  well  stirred  in  before 
adding  the  copper  hydroxid. 

Crude  Fiber. 

The  A.  O.  A.  C.  method  is  substantially  as  follows:  2  grams 
of  the  substance,  well  extracted  with  ether  (see  under  "Ex- 
traction"), are  mixed  in  a  500  c.c.  flask  with  200  c.c.  of  boiling 
water  containing  1.25  per  cent,  of  sulfuric  acid;  the  flask  is 
connected  with  an  inverted  condenser,  the  tube  of  which  passes 
only  a  short  distance  below  the  rubber  stopper  of  the  flask. 
The  liquid  is  brought  to  the  boiling-point  as  rapidly  as  possible 
and  maintained  there  for  30  minutes.  A  blast  of  air  conducted 
into  the  flask  may  serve  to  reduce  the  frothing  of  the  Hquid. 
The  mass  is  filtered,  washed  thoroughly  with  boiling  water 
until  the  washings  are  no  longer  acid;  the  undissolved  sub- 
stance rinsed  back  into  the  same  flask  with  the  aid  of  200  c.c. 
of  boiling  water  containing  1.25  per  cent,  sodium  hydroxid, 
nearly  free  from  sodium  carbonate;  again  brought  to  the 
boiling-point  rapidly  and  maintained  there  for  30  minutes  as 


ASH  39 

• 

directed  above.  The  liquid  is  filtered  by  means  of  a  Gooch 
crucible;  washed  with  boiling  water  until  the  washings  are 
neutral  to  phenolphthalein ;  dried  at  iio°;  weighed  and  incin- 
erated completely.     The  loss  of  weight  is  crude  fiber. 

The  filters  used  for  the  first  filtration  may  be  linen,  glass, 
wool,  asbestos,  or  any  form  that  secures  clear  and  reasonably 
rapid  filtration.  Hardened-paper  filters  may  serve.  The  sul- 
furic acid  and  sodium  hydroxid  must  be  made  up  of  the  specified 
strength,  determined  by  titration. 

Some  analysts  use  stronger  solutions.  Hehner  used  5  per 
cent,  acid  and  alkali.  It  would  be  convenient  if  normal  sul- 
furic acid  and  normal  sodium  hydroxid  were  adopted  as  solvents. 
It  is  probable  that  carbon  tetrachlorid  could  be  advantageously 
substituted  for  ether  in  the  preliminary  extraction. 

Crude  fiber  should  not  be  called  cellulose. 

Ash. 

The  ash  of  food  materials  may  usually  be  determined  by 
heating  several  grams  in  a  platinum  or  porcelain  crucible  at  a 
low  red  heat.  Higher  temperature  may  cause  loss  of  volatile 
salts — e.  g.,  chlorids.  If  a  white  ash  cannot  be  obtained  thus, 
the  material  should  be  heated  only  to  a  temperature  sufficient 
to  produce  charring,  the  charred  mass  thoroughly  extracted 
with  water,  and  the  insoluble  matter  collected  on  a  filter, 
which  may  then  be  returned  to  the  crucible  and  ashed.  To 
this  residue  the  filtrate  containing  the  soluble  matter  is  now 
added,  the  liquid  evaporated  to  dryness,  heated  to  low  red- 
ness, cooled,  and  weighed. 

A  muffle,  heated  by  gas,  will  often  be  very  useful  in  the 
incineration  of  organic  bodies.  A  light  draught  of  air  should 
be  maintained  during  the  operation. 

Ash  Soluble  in  Water. — The  ash  obtained  as  above  is  treated 
with  boiling  water,  the  solution  filtered  through  an  ashless 
filter,  and  the  filter  and  contents  again  ignited  and  weighed. 


40  FOOD  ANALYSIS 

The  soluble  ash  is  determined  by  difference.  If  desired,  the 
filtrate  may  be  filtered  to  dryness,  heated  just  below  redness, 
and  weighed.     The  first  method  is  the  most  convenient. 

Alkalinity  of  ash  is  often  an  important  datum.  It  will  differ 
with  the  indicator  used  and  whether  tested  by  direct  titration 
or  upon  the  portions  soluble  and  insoluble  in  water.  The 
following  method  will  furnish  data  of  value  in  many  cases. 

The  ash  is  mixed  with  water,  heated  nearly  to  boiling,  filtered 
and  washed  until  the  filtrate  measures  about  50  c.c.  An  in- 
dicator (phenolphthalein  is  usually  employed)  is  added  to  the 
filtrate  titrated  to  neutrality  with  ^  hydrochloric  acid.  Methyl 
orange  is  added  and  the  titration  carried  to  neutrality  again. 
The  filter  and  contents  are  dried,  ignited,  and  added  to  the 
residue  in  the  dish.  Excess  of  standard  acid  and  methyl 
orange  are  added  and  the  material  titrated  to  neutrality  with 
sodium  hydroxid. 

It  is  often  sufficient  to  titrate  the  ash  directly,  using  a  single 
indicator  and  not  separating  the  portions  soluble  and  insoluble 
in  water.     In  this  case  azolitmin  may  be  satisfactory. 

Ash  Insoluble  in  Acid. — ^The  residue  insoluble  in  water  is 
treated  with  hydrochloric  acid  and  the  portion  undissolved 
is  well  washed  on  the  filter  with  water,  dried,  ignited,  and 
weighed. 

The  ash  of  jats  is  conveniently  determined  by  the  following 
method :  A  weighed  quantity  is  melted  in  a  platinum  dish,  and 
a  smaller  filter,  free  from  ash,  is  folded  in  four,  placed  upright 
in  the  melted  fat,  and  lighted.     The  fat  is  quickly  burnt  off. 

The  following  is  a  compilation  of  methods  proposed  for  the  determination 
of  the  ash  of  sugars,  molasses,  honeys: 

(i)  5  to  10  grams  of  the  material  are  heated  in  a  platinum  dish  of  from  50  to 
100  c.c.  capactiy  at  100°  until  the  water  is  expelled,  and  then  slowly  over  a  flame 
until  intumescence  ceases.  The  dish  is  placed  in  a  muffle  and  heated  at  low  red- 
ness until  a  white  ash  is  obtained.  If  the  substance  contain  iron  or  any  other 
metal  capable  of  uniting  with  platinum,  a  dish  of  some  other  material  must  be 
used.    For  soluble  ash  the  ash  obtained  as- above  is  digested  with  water,  filtered 


EXTRACTION  WITH  MISCIBLE  SOLVENTS  4 1 

through  a  Gooch  crucible,  washed  with  hot  water,  and  the  residue  dried  at  100° 
and  weighed.     The  difference  of  weights  equals  the  soluble  ash. 

(2)  To  25  grams  of  molasses  or  50  grams  of  sugar,  50  mg.  of  zinc  oxid  are 
added,  and  the  mass  incorporated  thoroughly  by  adding  dilute  alcohol  and  mix- 
ing. It  is  then  dried  and  ignited  as  above.  The  weight  of  zinc  oxid  is  deducted 
from  the  weight  of  the  ash. 

(3)  The  mass  is  carbonized  at  low  heat,  the  soluble  salts  dissolved  with  hot 
water,  the  residual  mass  burned,  the  solution  of  soluble  salts  added,  and  evapo- 
rated to  dryness  at  100°,  ignited  gently,  cooled  in  a  desiccator,  and  weighed. 

(4)  The  sample  is  saturated  with  sulfuric  acid,  dried,  ignited  gently,  then 
burnt  in  a  muffle  at  low  redness.  One-tenth  of  the  weight  of  the  ash  is  deducted 
to  calculate  the  percentage. 

Extraction  with  Miscible  Solvents. 

For  thorough  extraction,  especially  with  difficultly'  soluble 
materials  and  volatile  solvents,  the  continuous  extraction  ap- 
paratus devised  by  Szombathy,  but  commonly  called  the  Soxhlet 
tube,  is  most  suitable. 

The  apparatus,  as  shown  in  figure  24,  is  provided  with  a 
globular  metal  condenser,  but  any  form  may  be  employed.  The 
material  may  be  placed  in  a  fat-free  paper  thimble  and  covered 
with  a  plug  of  cotton  to  prevent  loss  of  fine  particles.  In  place 
of  the  cotton  plug  a  Gooch  crucible  may  be  used,  as  shown  in  the 
cut!  The  top  of  the  thimble  should  be  a  short  distance  below, 
and  the  top  of  the  crucible  a  short  distance  above,  the  bend  of 
the  siphon.  The  thimble  should  be  supported  by  a  section  of 
glass  tubing,  i  to  2  cm.  long,  with  rounded  edges;  the  edge 
on  which  the  thimble  rests  should  be  a  little  uneven  to  prevent 
a  close  joint,  which  would  hinder  the  siphoning  of  some  of  the 
liquid. 

Another  method  is  to  use  a  glass  tube  open  at  both  ends,  the 
material  to  be  extracted  being  held  in  position  by  loose  plugs  of 
cotton  placed  above  and  below. 

Loss  of  solvent  by  leakage  often  occurs.     It  may  be  dim- 
inished somewhat  by  soaking  the  corks  in  rather  strong  hot 
gelatin  solution,  draining  them  quickly  and  then  exposing  them 
for  some  hours  to  formaldehyde  vapor. 
S 


42 


FOOD^ANALYSIS 


^ 


The  solvents  most  generally  employed  are  ether  and  petro- 
leum spirit,  but  chloroform,  carbon  tetrachlorid,  carbon  disulfid, 
benzene,  acetone  and  absolute  alcohol 
have  special  applications.  Carbon  tet- 
rachlorid is  well  adapted  for  extraction 
purposes  as  it  has  high  solvent  power 
and  is  not  easily  inflammable. 

When  extraction  is  completed,  the 
carton  and  materials  may  be  removed 
from  the  tube,  and,  replacing  the  parts  of 
the  apparatus,  much  of  the  solvent  may 
be  redistilled  into  the  extractor,  thus 
recovering  the  Hquid.  Care  must  be 
taken  not  to  distil  the  contents  of  the  flask 
closely  or  heat  strongly,  lest  some  of  the 
more  volatile  of  the  dissolved  matters 
pass  into  the  distillate. 

The  tedious  process  of  extraction  may 
often  by  replaced  by  direct  solution  as 
follows:  A  convenient  amount  of  the 
material,  finely  powdered,  is  placed  in  a 
flask,  a  definite  volume  of  solvent,  {e.  g. 
loo  c.c.)  poured  on,  the  flask  tightly 
corked,  the  mixture  gently  shaken  at 
convenient  intervals  for  some  hours,  and 
allowed  to  remain  in  overnight.  Care 
must  be  taken  that  the  solvent  does  not 
come  in  contact  with  the  cork.  The  mix- 
ture, after  standing,  is  again  shaken  a 
few  times,  allowed  to  settle  somewhat  and 
an  ahquot  part  (e.g.  50  c.c.)  rapidly  filtered 
off,  evaporated  as  usual  and '  weighed. 
The  process  is  adapted  for  use  with  shghtly  volatile  solvents 
such  as  alcohol,  but  with  care  may  be  used  with  ether,  petroleum 


Fig.  24. 


EXTRACTION  WITH  IMMISCIBLE  SOLVENTS 


43 


spirit,  and   carbon   tetrachlorid.     It  has  value  as  a  sorting 
method. 


Extraction  with  Immiscible  Solvents. 

Solvents  not  miscible  with  water  are  employed  for  extracting 
substances  by  shaking  the  solvent  thoroughly  with  the  aqueous 
solution,  allowing  the  liquids  to 
separate,  and  removing  one  of  them. 
The  process  is  most  conveniently 
performed  in  a  stoppered  separator. 
The  principal  difficulty  is  the  liabil- 
ity of  some  liquids  to  form  emulsions 
which  separate  only  after  long  stand- 
ing. Separation  may  sometimes  be 
hastened  by  cooling  the  mixture  or 
by  adding  more  of  the  solvent.  One 
of  the  most  satisfactory  methods 
when  operating  upon  small  amounts 
of  liquid  is  to  whirl  the  mixture  for 
a  short  time  in  a  high-speed  centri- 
fuge. 

Figure  25  shows  a  special  appa- 
ratus for  use  with  solvents  lighter 
than  water. 

The  cylinder  A  should  hold  about 
1000  c.c.  Two  openings  are  not 
necessary,  since  both  tubes  may  pass 

through  the  cork,  but  the  arrangement  shown  is  more  convenient. 
600  c.c.  of  the  solution  are  placed  in  the  cylinder,  300  c.c.  of 
solvent  added  and  the  mixtures  well  shaken.  The  rest  of  the 
apparatus  is  then  attached.  The  flask  B  has  a  capacity  of  200 
to  300  c.c. ;  the  solvent  in  it  is  heated  by  a  water-bath.  The 
vapor  passes  by  a  into  b,  the  condensed  liquid  flows  to  the 
bottom  of  A  and  rises  through  the  solution;   the  upper  layer 


Fig.  25. 


44 


FOOD   ANALYSIS 


returns  through  c  into  B.  The  tube  c  should  not  extend  into  the 
liquid  in  B.  A  small  quantity  of  aqueous  liquid  may  collect  at 
intervals  in  B  and  should  be  removed. 

Distillation  and  Sublimation. 

Retorts  and  alembics  are  now  but  little  used,  but  are  service- 
able in  some  cases.  With  glass  vessels  the  irregular  percussive 
boiling,  commonly  called  "bumping,"  is  liable  to  break  the 


Fig.  26. 


vessel  or  to  spurt  portions  of  the  undistilled  Hquid  into  the  con- 
densing apparatus.  This  may  often  be  prevented  by  the  ad- 
dition of  a  few  fragments  of  pumice,  clay  pipe,  or  platinum  foil. 
Dry  pumice  floats  on  most  liquids.  It  may  be  made  to  sink 
either  by  soaking  it  in  water  for  a  day  or  so  or  by  heating  the 
fragment  to  redness  and  quenching  it  in  the  liquid.     With 


DISTILLATION  AND  SUBLIMATION  45 

inflammable  liquids,  the  latter  method  must  be  used  cautiously. 
Bumping  may  often  be  prevented  by  using  the  burners  shown" 
in  figures  31  and  32. 

Condensing  apparatus  is  made  in  considerable  variety; 
Glass  and  block-tin  are  the  materials  for  tubes.  The  glazed 
porcelain  tubes  made  for  pyrometers  would  probably  be  well 
adapted  for  straight  condensing  tubes.  Glass  tubes  are  liable 
to  crack  at  the  point  at  which  the  cooling  action  begins.  To 
avoid  leakage  and  the  contact  of  hot  vapors  with  corks  or 
rubber  tubes,  the  connections  should  be  as  few  as  possible.  Fig- 
ure 26  shows  a  copper  tank  through  which  the  condensing  tube 
passes.  This  apparatus  is  especially  adapted  to  the  so-called 
** ammonia"  process  for  water-analysis.  The  neck  of  the 
retort  being  inclined  slightly,  as  shown,  causes  any  material 
thrown  into  it  to  return  to  the  boiling  liquid. 

Figure  27  shows  an  improved  form  of  distilling  apparatus 
devised  by  R.  S.  Weston.  The  condenser  tube  is  of  copper 
or  japanned  galvanized  iron.  The  details  of  construction  and 
arrangement  are  sufficiently  indicated  in  the  drawing.  The 
apparatus  is  shown  as  arranged  for  water  analysis.  When 
Kjeldahl  distillations  are  being  made  the  lower  end  of  the 
block-tin  tube  should  be  extended  by  means  of  a  bulbed  glass 
tube,  as  noted  elsewhere.  Safety  bulbs  may  also  be  placed 
between  the  flask  and  condensing  tube  in  such  a  way  as  to 
avoid  rubber- tube  connections.  Materials  are  added  by 
means  of  long-stemmed  funnels.  Weston  uses  a  Bunsen 
burner,  but  it  is  probable  that  the  burners  figures  31, 32,  would 
be  more  satisfactory. 

Figure  28  shows  Cribb's  condenser,  which  may  be  attached 
to  any  distiUing  apparatus.  The  distillation  tube  is  attached 
at  A.  The  walls  are  double;  condensation  occurs  in  the  space 
between  them,  and  the  distillate  flows  out  by  the  tube  E.  The 
cooling  water  flows  through  F  to  the  bottom  of  the  inner  space, 
overflows  at  J  into  the  catch-basin   below,  escaping  by  G, 


46 


FOOD   ANALYSIS 


The  stopper  /  serves  to  steady  the  tube  F,  and  should  have 
several  large  notches  cut  in  it  to  allow  the  water  to  escape  freely. 
It  is  usually  necessary  to  wrap  a  piece  of  muslin  around  the 


C/a/9t/o\ 


S*fpfiorf^  Ct^* 


Fig.  57. 


outside  of  the  apparatus  to  cause  the  overflowing  water  to  run 
properly.  The  condenser  may  be  made  of  glass,  block-tin, 
or  tinned  copper.     Experience  shows  that  the  apparatus  will  be 


DISTILLATION  AND  SUBLIMATION 


47 


more  satisfactory  if  some  of  the  dimensions  are  changed  from 
those  indicated  in  the  figure,  which  is  taken  from  Cribb's  paper. 
The  annular  space  should  be  larger,  especially  at  the  bottom; 
the  catch-basin  must  be  roomy,  and  G  should  have  a  caliber 
at  least  three  times  that  of  F.  The  catch-basin  is  held  in  place 
by  rubber  tubing.  The  condenser  is  supported  by  a  strong 
clamp.  L  is  for  attachment  of  an  air-pump  for  distillation 
under  diminished  pressure. 

Distillation  of  small  amounts  of  material  may  be  made 
with  the  ordinary  extractor,  terminating 
the  operation  before  the  distillate  reaches 
the  level  of  the  bend  of  the  siphon. 

For  many  distillations  the  simple  appa- 
ratus shown  in  connection  with  determin- 
ation of  the  volatile  acids  of  butter  will 
serve,  but  a  side-neck  flask,  as  shown 
in  figure  29,  is  more  generally  useful. 
In  this  figure  the  condensing  tube  is 
represented  relatively  too  short;  for  the 
volatilp  bodies  encountered  in  food  anal- 
ysis the  condenser  should  be  at  least  50 
cm.  long.  This  form  of  flask  permits  of 
introduction  of  materials  without  discon- 
necting the  apparatus  and  also  of  distilla- 
tion in  a  current  of  steam  or  of  indifferent 


gas. 


Fig.  28. 


For  distillation  in  a  current  of  steam,  a 
generator  is  needed.  A  Jena  flask  of  good  size  is  most  con- 
venient. It  should  be  provided  with  a  stopper  with  two 
tubes,  one  about  0.5  cm.  caliber,  reaching  to  near  the  bottom 
of  the  flask,  the  other  about  i.o  cm.  caliber,  reaching  just 
below  the  level  of  the  stopper.  The  latter  is  connected  with  a 
tube  passing  nearly  to  the  bottom  of  the  side-neck  flask.  The 
smaller  tube  in  the  generator  is  for  safety  in  case  of  obstruc- 


48 


FOOD  ANALYSIS 


tion.     Its  upper  opening  should  be  directed  so  that  no  damage 
will  be  done  if  the  hot  liquid  is  thrown  out. 

With  steam  distillation,  a  moderate  heat  should  be  maintained 
under  the  distillation  flask,  and  the  water  in  the  generator  kept 
boiling  actively.  The  junction  between  the  two  flasks  should 
be  by  tubes  which  touch  as  closely  as  possible,  held  by  a  rubber 
sleeve. 


Fig.  29. 

Inverted  Condenser. — For  prolonged  boiling  in  water  without 
concentration,  the  simplest  arrangement  is  a  flask  fitted  with  a 
cork  carrying  a  tube  about  2  meters  long.  The  lower  end 
should  be  cut  off  obliquely.  If  the  boihng  is  moderate,  the 
vapors  will  condense  and  run  back.  For  volatile  liquids  or 
special  cases,  regular  condensers  are  used.  The  ordinary 
straight  form,  made  of  glass,  is  usually  employed,  but  the  ball- 


APPARATUS   AND   CHEMICALS  49 

form,  shown  in  figure  24,  is  compact.  This  can  be  obtained  of 
glass. 

Fractional  distillation  is  best  carried  out  with  the  bulb-tubes 
devised  for  attachment  to  ordinary  flasks  so  that  the  vapor  may 
be  partially  condensed  and  succeeding  portions  washed  with 
the  liquid  which  runs  back  continuously  into  the  flask.  The 
most  used  are  the  Le  Bel-Heninger  and  Glynsky  tubes.  The 
former  bears  from  two  to  six  bulbs.  The  upper  part  has  an 
inclined  side  tube  for  connection  with  the  receiver  and  an 
opening  through  which  the  thermometer  can  be  passed.  Each 
of  the  bulbs  is  connected  with  the  one  just  below  by  a  side  tube. 
At  the  constricted  part  of  each  bulb  a  small  thimble  of  platinum, 
copper,  or  nickel  gauze  rests.  The  vapor  condenses  in  the 
cups  and  washes  the  vapor  subsequently  formed.  The  liquid 
runs  off  from  each  bulb,  back  to  the  flask.  The  flame  should  be 
regulated  so  as  to  keep  all  the  cups  full,  and  cause  the  distillate 
to  fall  from  the  end  of  the  tube  in  separate  drops.  In  the 
Glynsky  bulb,  glass  balls  replace  the  gauze. 

The  United  States  revenue-law  requires  all  distilling  ap- 
paratus to  be  registered,  no  matter  for  what  purpose  it  is  used. 
Heavy  penalties  are  imposed  for  using  non-registered  stills. 
No  fee  is  imposed  for  registry,  which  is  made  on  blanks  furnished 
by  the  Collector  of  Internal  Revenue. 

Sublimation  may  be  performed  in  a  narrow  test-tube  or 
watch-glasses  with  concavities  facing,  the  upper  glass  being 
slightly  small  so  that  it  may  fit  well.  A  gentle  heat  is  applied 
to  the  lower  dish.  By  substituting  a  beaker  containing  water 
for  the  upper  watch-glass  a  better  cooling  effect  will  be  ob- 
tained. 

Apparatus  and  Chemicals. 

These  can  now  be  obtained  generally  of  good  quality  at 
almost  all  times  and  places,  but  a  few  suggestions  may  be  of 
value. 

C 


FOOD   ANALYSIS 


Centrifuge. — Centrifugal  apparatus  is  of  much  advantage  in 
laboratory  work.  The  slow-speed  machines  made  for  milk 
analysis  are  of  limited  application;  much  better  results  are 
obtained  by  the  high-speed  apparatus  of  the  type  shown  in 
figure  30. 

In  operating  such  machines,  the  load  on  the  revolving  arms 
must  be  balanced  or  the  center  of  gravity  will  not  coincide 

with  the  center  of  revolution,  and 
an  objectionable  vibration  will  be 
produced.  The  machine  should  be 
attached  to  a  firm  table  or  shelf  and 
kept  properly  oiled  and  protected 
from  dust.  The  tubes  usually  fur- 
nished are  narrowed  at  the  bottom, 
and,  as  solid  material  is  apt  to  be 
packed  closely  by  the  centrifugal 
action,  it  is  sometimes  difficult  to 
J- ^,c..oK.r3fiill  dislodge  it,  but  care  should  be  taken 

to  get  all  such  material  out  of  the 
tube  so  as  not  to  contaminate  the 
substance  used  in  a  subsequent  ex- 
periment. If  it  be  desired  to  use 
vessels  not  narrowed  at  the  base, 
small  glass  tubes  closed  by  cork  at 
one  end  may  be  substituted.  In 
this  case,  however,  the  lower  end 
of  the  tube-holder  should  be  packed 
with  cotton  to  such  a  height  that  the  cork  cannot  be  driven  into 
a  part  of  the  tube  narrow  enough  to  hold  it  tightly.  If  this 
precaution  be  neglected,  the  rotation  will  push  the  glass  tube  so 
far  into  the  tube-holder  that  it  may  be  impossible  to  draw  it  out 
without  leaving  the  cork. 

Glassware  suitable  for  most  laboratory  work  is  now  made 
in  the  United  States,  but  the  Bohemian  and  Jena  glass  still 


Fig.  30. 


APPARATUS   AND  CHEMICALS  5 1 

shows  important  merit  which  will  lead  to  preference  for  it  in 
many  cases.  For  the  cleaning  of  glass  and  porcelain,  espe- 
cially when  working  with  fatty  matters,  the  commercial  triso- 
dium  phosphate  is  of  much  use.  Vessels  cleaned  with  it  must 
be  well  rinsed.  A  bath  of  so-called  battery  fluid  (potassium 
dichromate  or  sodium  dichromate,  or,  better,  the  crude  chromic 
acid  sold  for  the  purpose,  250  grams;  water,  2000  c.c;  sul- 
furic acid,  300  c.c.)  will  make  an  efficient  cleaning  solution  for 
all  non-metallic  articles.  These  should  be  cleansed  with  soap, 
sodium  phosphate,  or  sodium  carbonate  to  get  rid  of  the  greasy 
matters,  rinsed,  and  then  soaked  in  the  liquid  overnight.  The 
solution  gives  off  no  fumes  and  its  color  guards  against  imperfect 
rinsing.  It  is  of  little  value  when  it  has  become  brown  or 
green,  but  may  be  freshened  by  adding  crude  chromic  and 
sulfuric  acids.  As  the  liquid  is  very  corrosive,  all  waste  from 
it  should  be  washed  down  the  drain-pipes  with  a  free  flow 
of  water.  Strong  sulfuric  acid  is  used  by  some  chemists, 
especially  for  cleaning  greasy  apparatus.  Organic  materials 
such  as  corks  and  rubber  tubes  should,  of  course,  not  be  put  in 
these  cleaning  solutions. 

For  heating  beakers  and  flat-bottomed  flasks  the  hot-plate 
is  much  used,  but  the  thin  cast-iron  plates  commonly  furnished 
are  unsatisfactory.  A  better  form  is  a  rolled  plate  at  least  i 
cm.  thick.  Nickel  wire-gauze  is  a  good  substitute  for  the 
common  wire-gauze.  The  Chaddock  burner,  made  of  non- 
corrodable  materials,  is  now  obtainable,  and  is  adapted  to  use 
in  the  fume-box.  Electric  heating  apparatus  has  been  brought 
to  considerable  efficiency,  and  will  in  time  supplant  all  present 
methods,  but  the  installation  and  operation  are  as  yet  costly. 
An  incandescent  lamp  may  be  arranged  as  a  heating  apparatus, 
and  is  especially  satisfactory  in  extractions  and  distillations 
with  inflammable  materials.  The  low-temperature  burner  and 
evaporating  burner  shown  in  figures  31  and  32  are  convenient  in 
many  operations,  especially  in  heating  liquids  liable  to  bump. 


52  FOOD   ANALYSIS 

The  inlet  of  the  former  is  too  short;  it  should  be  lengthened 
by  a  piece  of  metal  tube,  or  the  rubber  connection  will  become 
hot.  In  default  of  this  lengthening  the  joint  may  be  kept  cool 
by  wrapping  around  it  a  piece  of  muslin,  the  ends  of  which  dip 
in  a  vessel  containing  water. 

Filter-papers  are  furnished  in  great  variety,  adapted  to  all 
purposes.  The  so-called  hardened  filters  are  serviceable  in 
several  operations,  such  as  determination  of  crude  fiber,  insolu- 
ble matter,  and  extraction  with  volatile  solvents,  for  with  care 
the  wet  precipitate  can  be  scraped  off  without  removing  an 
appreciable    amount    of    the    filter-paper.     Slightly    flattened 


Fig.  31.  Fig.  32. 

glass  rods  or  round  rods  bent  at  the  middle  to  an  obtuse  angle 
are  convenient  because  they  arc  not  liable  to  roll  off  of  beakers 
or  funnels. 

Reagents,  especially  those  used  only  in  small  amounts,  are 
most  conveniently  kept  in  capped  bottles,  each  with  small  glass 
tube  or  pipet,  the  tube  being  long  enough  to  reach  above  the 
top  of  the  bottle  (figure  17).  In  this  way  the  solution  will  not  get 
in  contact  with  the  neck  of  the  bottle.  Solids  should  be  kept  in 
hood-stoppered  bottles, — i.  e.,  those  in  which  the  fiat  top  of  the 
stopper  is  close  to  the  bottle, — so  as  to  give  less  chance  for  de- 
posit of  dust.  All  chemicals  in  general  use  should  be  kept  in 
closed  cases,  ammonium  hydroxid  and  ammonium  carbonate 


APPARATUS  AND  CHEMICALS  53 

being  separate  from  the  common  acids.  The  stock  bottles  for 
acids  and  standard  solutions  should  be  protected  from  dust 
by  placing  over  the  stopper  of  each,  an  inverted  tumbler  large 
enough  to  rest  on  the  top  of  the  body  of  the  bottle. 

Platinum  ware  requires  care  to'prevent  staining  and  crack- 
ing. Substances  containing  any  of  the  easily-reducible  metals 
must  not  be  heated  in  contact  with  platinum;  even  iron  com- 
pounds in  the  presence  of  reducing  agents — e.  g.,  filter-paper — 
will  do  harm.  Sudden  cooling  of  platinum  should  be  avoided, 
as  it  tends  to  make  the  metal  brittle.  After  being  heated  to 
redness  the  metal,  when  cold,  should  be  lightly  rubbed  with 
very  fine  sea-sand  (not  river-sand  nor  powdered  quartz  or 
pumice),  by  which  the  metal  will  be  burnished  and  its  texture 
preserved.  The  platinum-pointed  forceps  should  be  treated 
in  the  same  way. 

Platinum  dishes  may  often  be  cleaned  by  rubbing  them 
with  sodium  amalgam,  decomposing  this  by  immersion  in 
water,  and  driving  the  mercury  off  by  heating  to  redness. 
Some  stains  may  be  removed  by  melted  potassium  acid  sulfate. 

Nickel  dishes  may  be  substituted  for  platinum  in  cases  in 
which  only  gentle  heating  is  required,  but  nickel  is  apt  to  be 
injured  by  direct  heating  with  gas. 

For  lubrication  of  glass  stopcocks,  the  following  mixtures, 
devised  by  Phillips,  are  useful : 

Pure  rubber, 70  parts  Pure  rubber, 70  parts 

Spermaceti, 25     "  Unbleached  beeswax, ...  30      " 

Vaselin, 5     " 

The  rubber  must  be  fresh  and  pure;  rubber  scraps  will  not 
answer.  It  should  be  melted  in  a  covered  vessel,  the  other 
materials  added,  and  the  mixture  well  stirred  while  hot,  care 
being  taken  not  to  scorch  it.  It  must  not  be  exposed  to  air 
longer  than  is  necessary  during  heating,  and  should  be  kept 
in  well-closed  bottles.     These  mixtures  may  be  removed  from 


54  FOOD  ANALYSIS 

stopcocks  by  a  little  strong  nitric  acid  which  loosens  the  lubri- 
cant so  that  it  may  be  rinsed  off. 

All  the  largely  used  chemicals  are  obtainable  of  good  quality, 
as  a  rule,  but  in  important  investigations  tests  for  purity  and 
strength  should  be  applied.  The  following  notes  will  assist  in  this. 

Alcohol. — Ethyl  alcohol,  commonly  called  "grain  alcohol," 
contains  in  its  strongest  commercial  form  about  95  per  cent, 
of  ethyl  hydroxid,  notable  quantities  of  esters,  aldehydes, 
fusel  oil,  and  traces  of  acid.  For  some  purposes — e.  g.,  making 
standard  solutions  of  alkali — it  must  be  purified  by  redistilla- 
tion over  sodium  hydroxid.  The  absolute  alcohol  sold  by 
dealers  usually  contains  some  water.  The  presence  of  water 
in  alcohol  may  be  detected  by  the  evolution  of  acetylene  when 
a  little  calcium  carbid  is  added.  This  may  also  be  used  for 
removing  small  amounts  of  water,  the  liquid  being  redistilled, 
but  hydrogen  sulfid,  hydrogen  phosphid,  and  ammonium 
compounds  may  be  introduced.  Anhydrous  copper  sulfate 
is  turned  blue  by  alcohol  containing  water. 

Methyl  alcohol.  Crude  wood-alcohol  is  of  limited  use  in 
laboratory  work.  It  contains  much  acetone.  A  purified 
article  is  now  furnished,  under  the  trade  name  ''Columbian 
Spirit,"  which  is  about  98  per  cent,  methyl  hydroxid  and  is 
free  from  notable  amounts  of  impurities.  It  may  be  used 
with  economy  as  a  substitute  for  ethyl  alcohol  in  many  cases. 
It  is  more  volatile,  but  traces  of  strong-smelhng  foreign  matters 
may  cause  the  odor  to  persist  longer  than  with  refined  alcohol. 

Ether.  Commercial  ether  contains  notable  amounts  of  al- 
cohol and  water,  but  much  purer  samples  can  be  obtained  from 
dealers  in  laboratory  supphes.  To  obtain  good  results  with 
ether  it  is  essential  that  it  be  as  nearly  as  possible  free  from 
alcohol  and  water.  The  method  of  purification  recommended 
by  the  A.  O.  A.  C.  is  as  follows: 

Commercial  ether  is  washed  with  two  or  three  successive 
portions  of  distilled  water  and  soHd  sodium  hydroxid  added 


APPARATUS   AND   CHEMICALS  55 

until  most  of  the  water  has  been  extracted.  Carefully-cleaned 
metallic  sodium,  cut  into  small  pieces,  is  added  until  there  is  no 
further  evolution  of  hydrogen.  The  ether  thus  dehydrated 
must  be  kept  over  metallic  sodium,  and  should  be  only  lightly 
stoppered  in  order  to  allow  hydrogen  to  escape. 

Chlorojorm,  benzene,  petroleum  spirit  and  carbon  tetrachlorid 
are  usually  obtainable  of  good  quality.  All  are  liable  to  contain 
water.  This  may  be  removed  by  shaking  with  anhydrous 
calcium  sulfate  or  anhydrous  copper  sulfate  and  redistillation. 
Commercial  chloroform  is  liable  to  decomposition,  by  which 
it  becomes  acrid.  All  volatile  solvents  are  liable  to  contain 
appreciable  amounts  of  non-volatile  materials,  and  should  be 
tested  by  evaporating  a  measured  amount  and  weighing  the 
residue.  If  this  is  appreciable  the  solvent  should  be  distilled. 
Carbon  tetrachlorid  is  well  adapted  for  fat  extraction  when  an 
open  flame  is  used.  Light  petroleum,  commonly  known  as 
benzin  and  gasolin,  and  often  by  other  trade-names,  should  be 
purified  by  redistillation,  selecting  the  portions  which  distil  over 
below  50°. 

Sodium  hydroxid.  Several  brands  sold  for  household  use 
are  suitable  for  ordinary  purposes,  such  as  making  standard 
alkali  or  in  the  Kjeldahl- Gunning  process. 

Potassium  hydroxid.  The  specially  purified  grades  should 
be  used. 

Sand  and  asbestos  intended  for  moisture  and  extract  deter- 
mination must  be  selected  with  care,  and  dried  thoroughly 
before  weighing.  Common  sand  contains  much  material  other 
than  quartz ;  asbestos  fiber  is  often  of  inferior  quality. 

Indicators. — Numerous  indicators  have  been  proposed,  but 
for  ordinary  laboratory  work  litmus,  phenolphthalein,  and 
methyl-orange  are  usually  preferred. 

Litmus.  Litmus  solution  is  now  little  used,  but  azolitmin,  a 
pure  blue  color  obtained  from  it,  is  a  sensitive  indicator.  It  is 
freely  soluble  in  water  but  insoluble  in  alcohol.     The  solution 


56  FOOD  ANALYSIS 

must  be  kept  in  an  open  bottle.  Intermediate  litmus-paper, 
which  is  convenient  for  ascertaining  the  reaction  of  liquids,  is 
prepared  as  follows :  A  clear,  fresh  solution  of  litmus  is  divided 
into  two  equal  portions;  one  of  these  is  rendered  purple-red 
(not  bright  red)  by  the  cautious  addition  of  dilute  nitric  acid; 
the  other  portion  is  then  added  and  strips  of  good  filter-paper 
soaked  in  the  liquid  and  dried  quickly.  This  paper  will  be 
affected  by  ordinary  acid  or  alkaline  solutions.  It  should  be 
kept  in  the  dark,  protected  from  dust. 

Phenol phthalein.  A  solution  of  i  gram  in  100  c.c.  of  good 
(methyl  or  ethyl)  alcohol  is  sufficient  and  keeps  well. 

Methyl-orange.  A  solution  of  o.i  gram  in  100  c.  c.  water 
will  be  satisfactory.  In  titrating  with  methyl-orange  very  little 
of  the  indicator  should  be  used. 

Cochineal.  Many  prefer  this  indicator  for  titrating  am- 
monium hydroxid.  3  grams  of  powdered  cochineal  are  macer- 
ated for  several  days,  with  occasional  shaking,  in  100  c.c.  alcohol 
of  about  20  per  cent.,  and  the  solution  filtered. 

Starch  Indicator. — This  is  much  used  in  titrations  with 
iodin.  As  it  spoils  quickly,  it  is  usually  made  as  needed. 
Moerk  has  found  that  oil  of  cassia  acts  as  a  preservative  without 
interfering  with  the  efficiency  of  the  solution.  5  grams  of 
good  starch  (preferably  arrow- root)  are  mixed  with  about  100 
c.c.  of  cold  water,  and  the  mixture  poured  into  500  c.c.  of  boil- 
ing water  with  active  stirring.  The  liquid  is  allowed  to  cool, 
2  c.c.  of  oil  of  cassia  added,  made  up  to  1000  c.c,  shaken  and 
preserved  in  a  well-stoppered  bottle. 

Standard  acid. — The  strength  of  dilute  sulfuric  acid  can  be 
accurately  determined  by  adding  to  a  carefully  measured 
quantity  a  slight  excess  of  pure  ammonium  hydroxid,  evapora- 
ting in  a  platinum  basin  to  dryness  and  weighing  the  ammonium 
sulfate.  The  solution  to  be  valued  must  contain  nothing  but 
sulfuric  acid  and  water,  and  the  ammonium  hydroxid  must  be 
entirely  volatilized  by  evaporation  on  the  water-bath. 


APPLIED    ANALYSIS 
1 
GENERAL  METHODS 

POISONOUS   METALS 

The  elements  included  under  this  title  are  mercury,  arsenic, 
lead,  tin,  copper,  zinc  and  chromium.  Some  very  poisonous 
elements  not  likely  to  be  encountered  in  foods,  are  not  con- 
sidered in  this  connection. 

A.  H.  Allen  has  devised  a  general  process  for  the  detection 
of  poisonous  metals.  A  convenient  quantity  of  the  substance, 
say  25  grams,  is  mixed  by  degrees  with  sufficient  strong  sulfuric 
acid  to  moisten  the  mass  thoroughly  without  making  it  fluid. 
About  2  c.c.  will  generally  be  required.  Liquid  material  should 
be  evaporated  to  dryness  or  nearly  so  at  a  low  temperature 
before  being  treated  with  the  acid.  The  mass  is  heated  for  a 
short  time  on  the  water-bath,  after  which  the  temperature  is 
gradually  raised  to  a  point  just  below  that  required  to  volatilize 
the  sulfuric  acid,  and  maintained  until  the  action  seems  to  be 
complete.  It  is  not  necessary  to  carry  on  this  part  of  the  process 
until  all  the  carbon  is  burnt  off.  The  mass  is  allowed  to  cool, 
about  I  c.c.  of  strong  nitric  acid  added,  and  the  heating  con- 
tinued until  red  fumes  are  evolved.  Allen  recommends  the  use 
of  a  porcelain  crucible  in  these  operations,  but  the  Kjeldahl 
digestion  flasks  of  Jena  glass  would  probably  serve.  Recently 
ignited  magnesia,  in  the  proportion  of  0.5  gram  for  each  cubic 
centimeter  of  the  acid  used,  is  incorporated  with  the  mass  and 
the  mixture  burned  off  at  a  dull  red  heat,  preferably  in  a  muffle. 
After  cooling,  the  ash  is  moistened  with  nitric  acid,  again 
burned  off,  and  the  process  repeated  until  all  the  carbon  is  con- 

57 


58 


FOOD   ANALYSIS 


sumed.  The  residue  is  treated  with  0.5  c.c.  of  sulfuric  acid, 
heated  until  fumes  are  evolved,  cooled,  boiled  with  water, 
diluted  without  filtration  to  about  100  c.c,  saturated  with 
hydrogen  sulfid,  the  solution  filtered  and  examined  according 
to  the  following  scheme : 


Aqueous  Solution  may  contain  zinc  and  iron. 

Precipitate  and  Residue  may 

contain  lead 

Add  bromin  water  to  destroy  hydrogen  sulfid. 

sulfid,  stannic  oxid,  copper  sulfid,  or  calcium 

convert  iron  into  the  ferric 

state,  boil,  then 

sulfate.     Fuse  in  porcelain  crucible  for   lo 

add    excess   of    ammonium 

hydroxid,    boil 

minutes  with  2  grams  of  mixed   potassium 

again,  and  filter. 

and  sodium  carbonates  and  i  gram  of  sulfur. 
When  cool,  boil  with  water  and  fiher. 

Precipi- 

Filtrate if  blue,  contains  nickel. 

Residue.     Boil  with  strong  hy- 

Filtrate. 

tate  may 

Divide  into  two  portions: 

drochloric  acid  as  long  as  hy- 

Acidulate 

contain 

1 

drogen  sulfid  is  evolved,  add 

with  ace- 

iron (and 

a  few  drops  of  bromin  water 

tic     acid. 

p  h  0  s  - 

to  complete  the  oxidation  of 

A    yellow 

phates). 

the  copper  sulfid,  and  filter  if 
necessary.     To  the  filtrate  add 
excess  of  ammonium  hydroxid, 
when  a  blue  coloration  will  be 
indicative  of  copper.     Acidu- 
late the  Hquid  with  acetic  acid 

precip- 
itate  of 
stannic 
sulfid   in- 
dicates 

tin. 

and  divide  into  two  portions: 

I.  Heat  to  boil- 

n.     If   zinc 

I.     Add  potas- 

II.   Add  potas- 

ing  and  add 

found    in    I, 

sium  chro- 

sium   ferro- 

potassium 
ferrocyanid. 

for  its  deter- 

mate.    A  yel- 

cyanid.;    A 

mination, 

low     precipi- 

brownish 

White  pre- 

acidulate 

tate  indicates 

precipitate 

cipitate  or 

the  ammoni- 

lead. 

or  coloration 

turbidity   in- 

acal  solution 

indicates  cop- 

dicates zinc. 

strongly  with 
acetic  acid, 
filter,  if  nec- 
essary,   and 
precipitate 
the  zinc  from 
the  fihrate  by 
hydrogen  sul- 
fid.      Any 
nickel     pres- 
ent will  also 
b  e      precipi- 
tated. 

per. 

Allen's  scheme  does  not  include  chromium,  which  may  be 
present  as  a  constituent  of  lead  chromate  and  will  be  found 
almost  entirely  in  the  precipitate  and  residue  insoluble  in 
water.  For  its  detection  a  portion  of  this  or  of  the  original 
ash  should  be  fused  with  sodium  carbonate  and  potassium 
chlorate;  the  yellow  melt,  containing  chromate,  is  dissolved  in 


POISONOUS  METALS  59 

the  smallest  possible  quantity  of  water  and  slightly  acidulated 
with  hydrochloric  acid.  The  liquid  is  then  added  to  a  test- 
tube  containing  a  small  amount  of  hydrogen  dioxid  overlaid 
with  a  little  ether.  In  the  presence  of  a  chromate  the  water 
will  acquire  a  blue  color,  which  on  slight  shaking  will  pass 
into  the  ethereal  layer. 

When  iin  is  known  to  be  present,  the  amount  may  be  found 
by  treating  the  precipitate  of  stannic  sulfid  with  strong  nitric 
acid,  igniting  the  metastannic  acid  formed,  and  weighing  the 
resultant  stannic  oxid.  For  the  detection  of  tin  it  is  recom- 
mended to  treat  the  stannic  sulfid  with  hydrochloric  acid  and 
bromin  water  and  boil  the  filtered  liquid  with  iron  wire  to 
reduce  to  the  stannous  condition.  The  liquid  is  diluted  and 
decanted  from  the  undissolved  iron  and  any  precipitated 
material,  and  the  tin  detected  by  adding  a  drop  of  mercuric 
chlorid  solution,  which  will  produce  a  white  or  gray  turbidity 
according  to  the  amount  of  tin  present. 

Copper  may  be  estimated  colorimetrically  by  means  of 
ammonium  hydroxid  or  potassium  ferrocyanid.  According 
to  Bodmer  &  Moor,  for  very  small  amounts  the  ferrocyanid 
method  is  more  accurate.  Paul  &  Cownley  determine  copper 
as  follows:  The  sample  is  carbonized  in  a  platinum  dish  and 
extracted  with  a  little  hydrochloric  acid;  the  insoluble  residue 
is  ignited  with  a  little  nitric  acid,  hydrochloric  acid  added,  and 
the  resulting  mixture  added  to  the  original  extract.  The 
solution  is  then  concentrated  to  about  30  c.c,  placed  in  a 
weighed  platinum  dish,  and  the  copper  deposited  with  pure  zinc. 
If  the  deposit  is  not  of  true  copper  color,  it  is  dissolved  in  a  little 
nitric  acid  and  the  copper  determined  colorimetrically. 

Zinc. — Evaporated  fruits  are  liable  to  derive  zinc  from  the 
trays  on  which  the  drying  is  conducted.  Wiley  gives  the  follow- 
ing process  for  determination :  The  sample  is  placed  in  a  large 
platinum  dish  and  heated  slowly  until  dry  and  in  incipient  com- 
bustion.    The  flame  is  removed  and  the  combustion  allowed  to 


or  THE 

UMlVrDGi-r^ 


6o  FOOD  ANALYSIS 

proceed,  the  lamp  being  applied  from  time  to  time,  in  case  the 
burning  ceases.  The  mass,  when  burned  out,  consists  of  ash 
and  char.  It  is  ground  to  fine  powder  and  extracted  with 
hydrochloric  or  nitric  acid,  the  residual  char  is  burned  to 
whiteness  at  a  low  temperature,  the  ash  extracted  with  acid, 
the  soluble  portion  added  to  the  first  extract,  and  the  whole 
filtered.  A  drop  of  methyl  orange  solution  is  placed  in  the 
liquid  and  ammonium  hydroxid  added  until  it  is  only  faintly 
acid.  The  iron  is  precipitated  as  ferric  oxyacetate  by  adding 
50  c.c.  of  a  solution  of  ammonium  acetate,  250  grams  to  the  liter, 
and  raising  the  temperature  to  about  80°.  The  precipitate  is 
separated  by  filtration,  washed  in  water  at  80°  until  free  from 
chlorid,  the  filtrate  saturated  with  hydrogen  sulfid,  allowed  to 
stand  until  the  zinc  sulfid  settles,  and  poured  on  a  close  filter. 
It  is  often  necessary  to  return  the  filtrate  several  times  before  it 
becomes  limpid.  The  collected  precipitate  is  washed  with  a 
saturated  solution  of  hydrogen  sulfid  containing  a  little  acetic 
acid.  The  precipitate  and  filter  are  transferred  to  a  crucible, 
dried,  ignited,  and  the  oxid  weighed. 

Arsenic,  if  present  in  notable  amount,  may  be  detected  by 
ReinscWs  test,  a  liberal  amount  of  hydrochloric  acid  being  used, 
since  arsenates  do  not  otherwise  respond  to  the  test.  Some 
water  strongly  acidulated  with  hydrochloric  acid  is  placed  in  a 
test-tube,  about  half  a  square  centimeter  of  bright  copper  foil 
added,  and  the  liquid  boiled  gently  for  a  few  minutes.  If  the 
copper  remains  bright,  showing  that  the  reagents  contain  no 
arsenic,  the  material  to  be  tested  is  added  and  the  liquid  again 
boiled  for  several  minutes.  If  arsenic  be  present,  a  steel-gray 
stain  will  appear  on  the  copper.  The  slip  is  removed,  washed 
with  distilled  water,  dried  by  pressure  between  filter-paper, 
placed  at  the  closed  end  of  a  narrow  glass  which  has  been 
previously  dried  by  heating  nearly  to  redness.  The  tube  is 
gently  heated  at  the  point  at  which  the  copper  rests.  The 
arsenic  will  be  converted  into  arsenous  oxid,  which  will  collect  on 
the  cooler  portions  of  the  tube  in  octahedral  crystals. 


POISONOUS  METALS  6 1 

Reinsch's  test  cannot  be  applied  in  the  presence  of  active 
oxidizing  agents,   such  as   chromates,   chlorates,   or  nitrates. 

GutzeWs  test,  which  is  more  delicate,  is  as  follows:  Place 
in  a  tall  test-tube  about  a  gram  of  pure  zinc,  5  c.c.  of  diluted 
sulfuric  acid  (6  per  cent.),  and  i  c.c.  of  the  sample.  The 
mouth  of  the  test-tube  is  covered  with  a  tightly-fitting  cap  of 
three  thicknesses  of  filter-paper.  A  drop  of  strong  solution 
of  silver  nitrate  is  placed  on  the  upper  paper  and  the  tube 
allowed  to  stand  for  10  minutes  in  the  dark.  If  arsenic  be 
present,  a  bright  yellow  stain  will  appear  on  the  filter-paper^ 
which,  on  the  addition  of  water,  becomes  black  or  brown.  A 
blank  test  should  aways  be  made  to  establish  the  purity  of 
the  reagents.  Sulfids  (which  may  be  detected  by  substituting 
lead  acetate  for  the  silver  nitrate  in  the  above  test)  must  be 
oxidized  to  sulfates  before  applying  the  test. 

The  test  is  delicate.  A  less  rigorous  one  may  be  made  by 
substituting  a  drop  of  a  saturated  solution  of  mercuric  chlorid 
for  the  silver  nitrate.  If  no  yellow  coloration  appears  after  10 
minutes,  the  sample  may  be  considered  free  from  arsenic. 

The  purity  of  the  reagents  must  be  carefully  ascertained' 
before  applying  any  of  these  methods. 

For  the  detection  of  minute  amounts  of  arsenic.  Marsh's  test 
is  used.  The  details  as  given  by  Haywood  are  generally 
applicable. 

The  apparatus  consists  of  a  flask  holding  about  100  c.c,  with 
a  rubber  stopper  through  which  passes  a  long-stemmed  separa- 
tory  funnel — the  tube  of  which  should  reach  nearly  to  the 
bottom  of  the  flask — and  an  exit  tube  bent  at  a  right  angle. 
The  flask  should  stand  in  a  basin  containing  cold  water.  The 
exit  connects  with  a  bulb-tube  containing  a  small  amount 
of  lead  acetate  solution,  to  absorb  sulfur,  selenium,  and  tel- 
lurium. To  this  is  connected  a  calcium  chlorid  tube,  and, 
finally,  a  tube  of  very  resistant  glass,  about  20  cm.  long  and  not 
over  0.5  cm.  caliber.     It  must  be  drawn  out  to  nearly  capillary 


62 


FOOD   ANALYSIS 


narrowness  about  the  middle.  A  piece  of  fine  wire-gauze  is 
wrapped  around  the  tube  for  a  few  centimeters  on  the  wide  part 
nearer  the  flask.  The  gauze  must  not  reach  to  within  a  centi- 
meter of  the  narrow  part.  Two  Bunsen  burners  must  be  ar- 
ranged so  as  to  be  used  at  once  to  heat  the  gauze.  The  general 
arrangement  is  as  figure  33,  except  that  the  protecting  gauze, 
extra  burner  and  stem  of  the  separator  are  not  shown. 
The  burners  are  placed  so  that  the  flames  meet  and  the  gauze 
is  at  that  point.  The  bulb-tube  may  be  placed  in  water.  The 
extra-tube,  closed  by  a  pinch-cock,  is  convenient  but  not  neces- 
sary. If  used,  care  should  be  taken  that  the  pinch-cock  closes 
it  well. 


Fig.  33. 


For  use,  three  grams  of  arsenic-free  zinc  are  placed  in  the 
flask  and  then  30  c.c.  of  dilute  pure  sulfuric  acid  (i  to  8).  The 
apparatus  is  connected  and  the  hydrogen  allowed  to  flow  for 
15  minutes,  after  which  the  gauze  is  heated  strongly  for  20 
minutes.     No  deposit  should  appear  in  the  tube. 

The  prepared  material  (see  below)  is  placed  in  the  funnel  and 
gradually  run  into  the  flask.  The  action  is  continued  for 
about  an  hour,  the  portion  of  tube  within  the  gauze  being  kept 


POISONOUS  METALS  63 

very  hot  all  the  time.  The  tube  is  allowed  to  cool  and  the 
extent  and  appearance  of  the  deposit  compared  with  tubes  of 
known  value. 

The  sample  is  best  prepared  by  mixing  a  small  weighed 
portion  in  a  porcelain  basin  with  from  i  to  5  c.c.  of  a  mixture  of 
nitric  and  sulfuric  acids.  The  mass  is  heated  with  a  low  flame 
until  it  has  granulated  and  fumes  of  sulfuric  acid  are  not  abun- 
dant. The  charred  mass  is  broken  up,  mixed  with  a  little 
water,  and  boiled  to  get  rid  of  sulfurous  acid.  It  is  filtered,  the 
residue  washed,  and  the  filtrate  and  washings  made  up  to  a 
definite  volume  (about  40  c.c).  It  is  then  ready  for  the  de- 
termination. 

The  comparison  tubes  are  made  by  using  measured  volumes 
of  a  standard  solution  of  arsenous  oxid  in  such  amount  as  will 
contain  the  following  fractions  of  a  milligram  of  elementary 
arsenic  J  operating  with  each  solution  as  directed  above:  0.005; 
o.oi;  0.02;  0.03;  0.04;  0.05;  0.06;  0.07.  These  deposits 
(mirrors)  should  be  sealed  and  kept  in  the  dark.  Even  then 
they  fade,  and  for  accurate  observation  should  not  be  over  three 
weeks  old. 

.  The  standard  solution  is  made  by  dissolving  o.oi  32  gram  of  dry 
pure  arsenous  oxid  and  o.i  gram  pure  sodium  acid  carbonate, 
in  100  c.c.  of  water.  The  mixture  is  kept  hot  until  the  arsenous 
oxid  is  dissolved,  cooled,  slightly  acidified  with  sulfuric  acid, 
and  made  up  to  1000  c.c.  Each  c.c.  of  this  solution  contains 
0.00001  gram  of  elementary  arsenic.  Aliquot  portions  are  used 
for  making  the  standard  mirrors. 

As  this  test  is  extremely  delicate,  great  care  must  be  taken  to 
ensure  purity  of  all  reagents.  It  must  be  borne  in  mind  that 
most  natural  substances  will  give  slight  reactions  for  arsenic 
by  it. 

All  junctions  must  be  as  tight  as  possible.  The  connected 
points  of  the  different  pieces  should  be  of  the  same  diameter  and 
the  junctions  made  by  short,  close-fitting,  pure  rubber  tubing. 


64  FOOD   ANALYSIS 

Great  care  must  be  taken  that  the  apparatus  is  thoroughly 
cleaned  between  each  use.  In  cases  in  which  the  results  are  to 
be  used  in  criminal  prosecutions  the  apparatus  should  be  new. 


COLORS 

At  present,  the  colors  used  in  food-articles  are  mostly  synthetic 
products,  commonly  called  "anilins,"  but  largely  derived  from 
other  coal-tar  materials. 

Natural  organic  colors — annatto,  cochineal,  turmeric,  indigo, 
saffron,  and  chlorophyl — are  used  to  a  limited  extent,  but 
mineral  colors  are  rarely  employed.  Ferric  oxid  is  used  in 
some  chocolate  substitutes. 

The  identification  of  individual  colors  in  mixture  with  foods 
or  beverages  is  difficult,  often  impossible,  with  methods  at 
present  available.  It  is  possible  in  many  cases  to  distinguish 
between  artificial  and  natural  colors.  The  following  method  is 
generally  applicable  for  distinction  between  these  classes. 

Pure  white  wool  (the  material  known  as  ''nun's  veiling" 
is  satisfactory)  is  cleaned  by  boiling  for  a  short  time  in  soap- 
suds, washed  thoroughly  with  water,  well-dried,  and  cut  into 
slips  about  3  X  10  cm.     They  should  be  kept  in  a  closed  bottle. 

A  convenient  quantity  of  the  material,  depending  on  the 
amount  of  color,  is  placed  in  a  beaker.  For  ordinary  liquids, 
100  c.c.  will  suffice;  for  soHds  and  semi-solids  from  5  to  25 
grams.  In  the  latter  case,  water  should  be  added  to  make  the 
bulk  about  100  c.c.  The  beaker  is  placed  in  a  water  bath,  i  c.c. 
of  hydrochloric  acid  added  and  a  slip  of  the  cleaned  wool.  The 
liquid  is  kept  in  the  boihng  water  for  a  moderate  time.  If  not 
appreciably  dyed  in  fifteen  minutes  it  may  be  assumed  that  no 
coal-tar  color  is  present.  In  most  cases,  however,- some  color 
will  be  imparted,  even  if  only  natural  colors  are  present.  The 
slip  is  washed  well  with  cold  water,  warmed  for  a  few  minutes 
in  very  dilute  hydrochloric  acid,  again  washed  well,  and  im- 


COLORS  65 

mersed  in  about  25  c.c.  of  water  to  which  2  c.c.  of  strong 
ammonium  hydroxid  have  been  added.  By  this  means,  the 
color  will  generally  be  dissolved  promptly  from  the  slip,  but  it 
may  be  necessary  to  allow  much  longer  action.  When  the  cloth 
is  nearly  or  quite  decolorised,  it  is  taken  out  of  the  liquid.  The 
latter  is  diluted  to  about  50  c.c,  rendered  moderately  acid  by  ad- 
dition of  hydrochloric  acid,  another  slip  of  cleaned  wool  im- 
mersed and  the  liquid  heated  in  the  water  bath.  Coal-tar 
colors  and  some  lichen  colors  (archil,  cudbear,  litmus)  will  give 
marked  second  dyeing. 

Lichen  colors,  including  a  sulfonated  orcein,  now  often 
used  in  food  articles,  are  distinguished  by  Tolman's  method,^ 
depending  on  the  fact  that  amyl  alcohol  removes  them  from 
the  ammonium  hydroxid  solution.  If,  therefore,  a  double  dye  - 
ing  is  obtained,  the  process  should  be  repeated,  but  the  am- 
monium hydroxid  solution  should  not  be  acidified  but  shaken 
with  pure  amyl  alcohol.  If  this  acquires  a  purplish  red  tint,  it 
is  evaporated  on  the  steam  bath,  the  residue  dissolved  in  water 
and  the  solution  mixed  with  a  little  tin  and  hydrochloric  acid. 
Lichen  dyes  are  bleached  by  this  method  and  are  restored  by 
ferric  chlorid.  These  reactions  exclude  all  azo-dyes  and  ma- 
genta. 

Some  tests  adapted  specially  to  the  recognition  of  colors  in 
particular  foods  will  be  described  in  connection  with  such  foods. 

When  dyes  intended  for  food-coloring  are  to  be  examined 
in  bulk,  the  following  methods  are  advantageous : 

A  small  quantity  of  the  sample  (o.i  to  0.25  gram)  is  heated 
on  platinum  foil.  Nitro-colors  show  more  or  less  deflagra- 
tion at  first.  Sulfonated  colors  form  a  fusible  residue,  in 
which  the  carbon  bums  with  difficulty.  It  will  be  advanta- 
geous to  add  some  oxidizing  agent  (potassium  nitrate,  potas- 
sium chlorate,  or  sodium  nitrate).  It  is  not  necessary  to 
bum  off  all  the  carbon.  The  mass  is  allowed  to  cool,  boiled 
up  with  water  acidulated  with  hydrochloric  acid  (this  may 
7 


66  FOOD  ANALYSIS 

cause  the  evolution  of  a  little  hydrogen  sulfid),  and  barium 
chlorid  added.  A  copious  white  precipitate  will  occur  if  the 
color  is  a  sulfonated  one. 

For  detection  of  arsenic  the  Reinsch  test  may  be  applied  or 
the  color  may  be  examined  for  all  the  important  poisonous 
metals  by  the  scheme  given  on  page  58. 

Identification  of  colors  may  sometimes  be  accomplished  by 
routine  methods,  several  of  which  are  given  in  the  following 
pages.  The  first  is  Green's  adaptation  of  Weingartner's  tables. 
It  is  reproduced  without  modification  of  spelling  or  nomenclature 
from  Allen's  '' Commercial  Organic  Analysis,"  edited  by 
Matthews.     The  reagents  required  are  as  follows: 

Tannin  solution.  Tannin,  i  gram ;  sodium  acetate,  i  gram ; 
water,  10  c.c. 

Zinc  dust. 

Dilute  hydrochloric  acid:  Hydrochloric  acid,  5  c.c;  water, 
15  c.c. 

Ammonium  hydroxid  solution. 

Chromic  acid  solution:  Chromium  teroxid,  i  gram;  water, 
100  c.c. 

Chromic- sulfuric  acid  solution:  Chromium  teroxid,  i  gram; 
strong  sulfuric  acid,  2.5  c.c..*  water,  100  c.c. 

Strong  sodium  hydroxid  solution:  Sodium  hydroxid,  33 
grams;  water,  67  c.c. 

Dilute  sodium  hydroxid  solution:  Sodium  hydroxid,  5  grams ; 
water,  95  c.c. 

Alcohol.     70  per  cent. 

In  applying  the  scheme  a  primary  division  is  made  into 
dyes  soluble  and  insoluble  in  water.  The  former  are  divided 
by  means  of  the  tannin  solution  into  the  so-called  basic  and 
acid  groups.  The  dyes  which  in  aqueous  solution  are  pre- 
cipitated by  tannin  solution  are  termed  basic  dyes. 

The  reduction  with  zinc  dust  is  best  made  by  adding  a  little 
of  the  zinc  dust  to  the  hot  dyestuff  solution  contained  in  a 


COLORS  67 

test-tube,  agitating,  and  adding  dilute  hydrochloric  acid  drop 
by  drop  until  decolorized.  Excess  of  acid  should  be  care- 
fully avoided.  When  the  color  acid  is  quite  insoluble,  the 
reduction  is  made  with  zinc  dust  and  ammonium  hydroxid. 
The  reduced  solution  is  decanted  upon  a  small  filter;  if  the 
color  does  not  return  in  a  few  minutes,  the  paper  is  moistened 
with  chromic  acid  solution.  In  the  case  of  acid  colors  the 
chromic-sulfuric  acid  solution  should  be  used.  As  some  dyes 
do  not  show  their  color  in  presence  of  free  acids,  the  paper 
should  be  exposed  to  the  fumes  of  strong  ammonium  hydroxid 
solution  before  deciding  as  to  whether  the  color  will  return. 


68 


FOOD   ANALYSIS 


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COLORS 


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70 


FOOD   ANALYSIS 


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COLORS  71 

rota's  scheme  for  recognition  of  colors^ 

Two  special  reagents  are  used. 

Stannous  chlorid  10  per  cent,  solution  in  hydrochloric  acid. 

Potassium  hydroxid  20  per  cent,  solution  in  water. 

The  material  may  be  tested  in  solution  in  water  or  alcohol. 
It  should  be  diluted  with  water  or  alcohol,  as  required,  until  the 
color  is  not  deep.  Turbid  liquids  njust  be  filtered.  A  com- 
parison test  of  the  solution  should  be  made  with  hydrochloric 
acid  alone,  as  many  effects  of  the  stannous  chlorid  reagent  are 
due  to  the  acid  and  not  to  the  tin  compound.  Some  colors 
require  considerable  time  to  effect  a  change. 

To  a  portion  of  the  solution  a  small  amount  of  stannous  chlorid  reagent 
is  added,  the  mixture  shaken  and  heated  to  boiling.  The  same  test  is  applied 
to  another  portion,  using  hydrochloric  acid  alone. 

1 .  The  stannous  chlorid  decolorizes  the  liquid  (see  A) . 

2.  The  color  is  not  affected  more  than  by  hydrochloric  acid  alone  (see  B). 

A.  The  liquid  is  mixed  with  either  ferric  chlorid  or  hydrogen  dioxid 

or  is  shaken  with  air. 

The  color  does  not  return.  Nitro-,  nitroso-,  azo-  and  hy- 
drazo-colors.  Picric  acid, 
naphthol  yellow,  Ponceau, 
Bordeaux,  Congo-red. 

The  color  is  restored.  Indogenid,  imido-quinones> 

methylene  blue,  safranin, 
indigo-carmine. 

B.  A  part  of  the  original  solution  is  mixed  with  some  of  the  potassium 

hydroxid  and  warmed. 

The  liquid  is  decolorized     Amido-derivatives    of    di-    and 
or  rendered  turbid.  triphenylmethane,     auramins, 

acridins,  quinolins  and  colois 
from  thiobenzinil. 
The  reagent  produces  no 
discoloration  or  turbid- 
ity. Monamid,         diphenylmethane, 
oxyketone,  eosins,  aurin,  aliz- 
arin and  most  natural  colors. 

Many  of  the  powders  and  pastes  sold  for  imitating  natural 
vegetable  colors  are  mixtures  of  several  coal-tar  colors  often 


72  FOOD  ANALYSIS 

representing  several  types,  so  that  the  above  schemes  will  give 
confusing  results.  The  identification  of  the  ingredients  of  such 
mixtures  can  generally  be  done  only  by  expert  color-chemists, 
but  some  information  may  be  obtained  by  dyeing  successive  por- 
tions of  wool  in  the  same  bath.  The  color  with  the  strongest 
attraction  is  taken  out  in  greater  amount  in  the  first  dyeing,  and 
a  series  of  dyed  slips  will  be  obtained  showing  the  principal 
tints  of  the  mixture.  Information  is  also  often  gained  by  dye- 
ing in  different  baths.  The  color  material  to  be  tested  is  made 
up  with  about  loo  c.c.  of  water,  a  few  grams  of  sodium  sulfate 
and  2  c.c.  of  strong  sulfuric  acid.  Another  bath  is  made  with 
a  few  grams  of  alum  in  loo  c.c.  of  water.  A  separate  piece  of 
wool  is  dyed  in  each  bath.  If  more  than  one  color  is  pres- 
ent a  notable  difference  in  the  dyeing  may  be  obtained. 

The  following  process  for  cochineal  is  due  toGirard  &  Dupre:^ 
The  material  is  dissolved  in  water  if  not  already  in  solution, 
moderately  acidulated  with  hydrochloric  acid,  and  shaken  out 
with  amyl  alcohol.  If  cochineal  is  present,  the  alcohol  will  be 
colored.  It  is  separated,  washed  with  water  until  neutral  and 
divided  into  two  portions.  To  one,  a  dilute  solution  of  uranium 
acetate  is  added.  Cochineal  produces  a  characteristic  emerald 
green.  To  the  other  portion  is  added  a  little  ammonium  hy- 
droxid.  Cochineal  gives  a  violet  solution,  but  this  reaction  is 
not  characteristic,  as  it  is  given  by  many  fruit  colors.  See  also 
pages  65  and  74,  and  the  detection  of  carmine  in  meat,  under 
''Flesh  Foods." 


COLORS  73 

For  the  detection  of  colors  used  in  egg  substitutes,  Winton  & 
Bailey  give  a  special  scheme:^ 

The  material  is  treated  with  95  per  cent,  alcohol. 

A.  The  color  dissolves. 

1.  Filter-paper  is  dipped  in  the  solution,  dried,  moistened  with  a 

mixture  of  hydrochloric  and  boric  acids  and  again  dried. 
b.  The  color  becomes    cherry-red,  changed  to  grayish-blue  on 
addition  of  ammonium  hydroxid.  Turmeric. 

2.  The  color  is  not  affected  by  these  reagents. 

a.  The  alcoholic  solution  on  evaporation  leaves  a  deposit  soluble 

in  water;    the  solution  is  partly  decolorized  by  hydrochloric 
acid.  Nitro-colors. 

b.  The  deposit  from  alcohol  is  soluble  in  water.      True  egg  color. 

B .  The  yellow  color  is  not  soluble  in  the  alcohol. 

I.  The  material  is  treated  with  a  mixture  of  90  per  cent,  of  alcohol 
and  10  per  cent,  hydrochloric  acid. 
It  dissolves  with  an  orange  color.     Filter-paper  dipped  in  this 
and  dried   becomes  rose-red  on  drying  at  room-tempera- 
ture. Azo-colors. 

The  annexed  synopsis  of  reactions  of  natural  colors  with  some 
common  color- reagents  is  from  results  obtained  by  La  Wall  from 
authentic  samples.  The  ammonium  hydroxid,  hydrochloric 
acid  and  stannous  chlorid  are  the  ordinary  laboratory  solutions, 
added  in  small  amounts  to  water-solutions  of  the  color.  The 
other  reagents  are : 

1.  Double  dyeing  as  described  on  page  64.  The  figures  refer  to  the  order 
of  the  dyeing.  "Amm"  following  abbreviation  of  a  color-name,  means  the 
effect  produced  by  ammonium  hydroxid  on  the  first  dyeing.  As  a  rule,  second 
dyeing  gave  no  noteworthy  effect. 

2.  Good  kaolin  was  shaken  with  a  portion  of  the  solution  and  the  liquid 
filtered. 

3.  A  piece  of  zinc  was  dropped  into  the  hydrochloric  acid  solution  of  the 
color. 


74 


FOOD   ANALYSIS 


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76  FOOD  ANALYSIS 

PRESERVATIVES 

The  decomposition  of  food  is  prevented  by  sterilization  or 
by  addition  of  preservatives.  Some  preservatives — e.  g.,  com- 
mon salt,  niter,  acetic  acid,  and  wood  smoke — have  been  known 
from  early  times  and  are  still  in  vogue.  Among  the  more 
important  of  the  newer  forms  are  salicylic  acid,  benzoic  acid, 
sodium  benzoate,  beta-naphthol,  saccharin,  abrastol,  formal- 
dehyde, fluorids,  silicofluorids,  sulfites,  boric  acid,  and  borax. 
Others,  mostly  synthetic  coal-tar  derivatives,  have  been  sug- 
gested and,  to  a  limited  extent,  used.     Most  acids  are  antiseptic. 

Each  of  the  substances  above  named  has  special  adap- 
tabilities; some  of  them  are  widely  applicable,  and  hence  are 
largely  used.  The  permissible  food-preservatives  are  not 
distinctly  germicidal  and  must  remain  in  the  food  if  continued 
preservation  is  desired. 

Salicylic  acid  is  a  white  crystalline  powder,  soluble  in  500 
parts  of  cold  water,  more  freely  in  alcohol.  Ether,  petroleum 
spirit,  chloroform  and  carbon  tetrachlorid  dissolve  it  readily 
and  remove  it  from  an  acidified  water-solution.  It  distils  in  a 
current  of  steam.  Its  most  characteristic  reaction  is  the  violet 
produced  by  ferric  salts. 

Salicylates  exist  normally  in  many  vegetable  substances;  in 
a  few  in  considerable  amount,  in  many,  such  as  common  edible 
berries,  in  very  small  amounts,  but  still  recognizable  by  delicate 
tests.  Care  must  be  taken  therefore  in  interpreting  the  results 
of  such  tests. 

Sodium  benzoate  is  usually  sold  as  a  granular  white  powder 
which  has  a  slight  aromatic  odor  and  a  nauseous  taste.  It  is 
freely  soluble  in  water.  In  the  United  States  it  is  the  usual 
preservative  for  catsups,  jams,  jellies,  mince-meat,"  and  pre- 
serves. 

.  .  Benzoic  acid  is  not  frequently  used  in  food  articles,  but  some 
of  it  may  be  formed  from  sodium  benzoate  by  the  action  of  acids 
or  acid  salts  in  the  food. 


PRESERVATIVES  77 

Saccharin.  Commercial  saccharin  is  somewhat  variable  in 
composition.  It  is  a  white,  crystalHne,  intensely  sweet  powder, 
soluble  in  looo  parts  of  cold  and  loo  parts  of  boiling  water. 
It  is  more  soluble  in  alcohol,  glycerol,  and  ether,  and  very 
slightly  soluble  in  chloroform,  benzene,  and  petroleum  spirit. 
Ether  removes  it  from  its  aqueous  solutions.  Pure  saccharin 
is  slightly  volatile  at  ioo°  and  leaves  no  ash,  but  impurities  may 
be  present  in  the  form  of  sodium  salts,  and  considerable  ash, 
principally  sodium  sulfate,  may  be  left  upon  ignition. 

,3-naphthol  is  a  white  crystalHne  powder,  shghtly  soluble  in 
water,  freely  in  alcohol,  ether,  chloroform,  benzene,  fats,  and 
alkaline  solutions.  It  is  wholly  volatile  on  ignition.  It  is 
liable  to  contain  small  amounts  of  a-naphthol.  The  so-called 
hydronaphthol  is  substantially  the  same  as  i9-naphthol. 

Ahrastol  or  asaprol  (calcium  /5-naphthol-a-monosulfonate) 
is  a  colorless  or  light  reddish  powder  freely  soluble  in  water  and 
alcohol.  In  dilute  solution  in  water  it  produces  with  a  solution 
containing  mercuric  nitrate  and  nitric  acid,  a  canary-yellow 
liquid.     Stronger  solutions  produce  a  yellow  precipitate. 

.Formaldehyde  is  a  gas  freely  soluble  in  water,  from  which 
solution  a  polymeric  modification  is  easily  obtained  as  a  white 
solid,  volatilized  only  at  a  temperature  above  the  boiling- 
point  of  water.  Formaldehyde  is  principally  sold  as  a  40  per 
cent,  watery  solution  designated  by  the  copyrighted  name 
''formahn."  More  dilute  solutions  are  sold  under  a  variety 
of  fanciful  and  misleading  names.  The  40  per  cent,  solution 
is  a  colorless  liquid  with  a  slight,  somewhat  acrid  odor  and 
a  faint  acid  reaction,  the  last  property  being  probably  due  to 
small  amounts  of  formic  or  acetic  acid  produced  by  oxida- 
tion. When  this  solution  is  boiled,  most  of  the  formaldehyde 
distils  readily  with  the  steam;  but  if  the  fresh  distillate  be 
evaporated  at  a  lower  temperature, — as,  for  example,  on  a 
shallow  dish  placed  over  boiling  water, — a  large  part  is  con- 
verted into  the  solid  form.     All  the  modifications  of  formalde- 


78  FOOD   ANALYSIS 

hyde  have  active  reducing  qualities  and  exhibit  strong  tendency 
to  combine  with  proteids  so  as  to  form  insoluble  bodies.  In 
the  preservation  of  food,  the  commercial  formalin  is  almost  ex- 
clusively used. 

Sulfites.  The  acid  salts  are  more  active  than  the  neutral 
form  and  are  more  used.  Calcium  sulfite  is  also  frequently 
employed.  Sulfites  are  white  solids  freely  soluble  in  water 
and  glycerol,  but  not  appreciably  in  alcohol,  or  the  solvents 
immiscible  with  water.  Their  antiseptic  action  being  strongly 
exerted  upon  yeast,  they  have  been  used  largely  to  control  or 
prevent  alcoholic  fermentation.  The  detection  of  sulfites 
being  based  upon  the  recognition  of  the  sulfurous  acid  derived 
from  them,  a  specific  description  of  each  will  not  be  needed. 

Boric  acid,  Borax.  A  mixture  of  these  is  frequently  sold 
under  trade  names,  such  as  ''  Preservaline  "  and  "  Rex  Magnus." 
They  are  also  used  separately.  Both  are  white  powders  soluble 
in  water;  borax  is  practically  insoluble  in  alcohol,  boric  acid 
freely  soluble.  Both  are  non- volatile  at  a  red  heat,  but  a  watery 
solution  of  boric  ac* '  ■  tnnot  be  evaporated  without  considerable 
of  the  acid  passing  A  with  the  steam.  Borax  has  an  alkaline 
reaction;  boric  acid  is  acid  to  litmus,  but  turns  turmeric  paper 
brown  when  its  solution  is  evaporated  on  it. 

When  boric  acid  is  heated  with  glycerol,  tritenyl  borate  is 
produced  as  a  thick  sirup  miscible  in  all  proportions  with  cold 
water  and  decomposed  by  hot  water.  By  evaporation  it  can 
be  obtained  in  the  form  of  a  transparent,  glassy,  brittle  mass 
which  absorbs  water  readily.  A  preparation  made  by  dissolv- 
ing borax  in  glycerol  has  also  been  offered  as  a  preservative, 
but  is  little  used.  These  glycerol  preparations  have  been  sold 
under  various  names,  such  as  ''boroglyceride"  and  "glyceride 
of  boric  acid." 

Borates  are  present  in  appreciable  amount  in  many  fruit- 
juices. 

FluoridSj  borofluorids,  and  silicofluorids.     The  sodium,  potas- 


PRESERVATIVES  79 

slum  and  ammonium  compounds,  have  been  principally  used, 
being  among  the  few  forms  soluble  in  water.  They  are  white 
powders,  not  volatile  at  a  red  heat  except  ammonium  fluorid. 
The  last  has  been  sold  under  the  riame  "antisepticum." 

Detection  of  Preservatives. — Owing  to  the  difference  in 
the  chemical  character  of  preservatives  and  of  the  food  articles 
in  which  they  are  used,  few  general  methods  can  be  given;  the 
examination  must  be  conducted  with  reference  to  the  material 
likely  to  be  present.  The  following  are  suggestions  in  this 
direction:  In  meats,  boric  acid  and  sulfites;  in  milk  and  milk 
products,  formaldehyde  and  boric  acid,  occasionally  salicylic 
acid.  In  jams,  jellies,  mince-meat,  and  table  dehcacies,  benzoic 
and  salicylic  acids  or  their  salts;  occasionally  boric  acid.  In 
cider  and  some  other  fruit  juices,  salicylic  acid  and  sulfites.  In 
fermented  beverages  and  malt  extracts,  salicylic  acid,  sulfites, 
fluorids,  silicofluorids,  borofluorids ;  abrastol  may  be  employed, 
but  the  data  in  regard  to  it  are  limited.  Saccharin  is  likely  to 
be  present  in  beer*,  wines,  and  sweetened  articles. 

Several  preservatives  are  easily  extractt '  '  ^m  food  articles  by 
shaking  with  ether  which  dissolves  them.  The  solution  should 
be  slightly  acid.  If  not,  a  little  sulfuric  acid  should  be  added. 
If  the  extraction  be  repeated  with  several  portions  of  the  solvent 
an  approximate  quantitative  determination  may  be  made.  The 
shaking  must  be  vigorous,  so  as  to  bring  the  solvent  in  contact 
with  all  parts  of  the  sample.  In  many  cases  this  will  produce  an 
emulsion  which  separates  very  slowly.  The  application  of  the 
centrifugal  method  will  be  useful  in  this  case.  The  addition  of 
more  of  the  solvent  and  the  cooling  of  the  material  is  also 
advised. 

The  following  descriptions  are  adapted  especially  to  the 
conditions  under  which  the  different  preservatives  are  likely 
to  be  found.  As  they  are  somewhat  soluble  i^  water,  solid 
or  semi-solid  materials  may  be  exhausted  with  vvater  and  the 
liquid  concentrated  at  a  low  temperature.     In  many  cases  the 


8o  FOOD   ANALYSIS 

sample  may  be  strained  through  muslin  and  the  tests  applied  to 
the  filtrate. 

The  volatility  of  some  preservatives,  especially  in  a  current 
of  steam,  is  occasionally  serviceable.  Formaldehyde  may  be 
thus  obtained  from  milk.  Benzoic  acid,  saccharin  and  sulfites 
may  be  separated  by  mixing  about  200  grams  of  the  sample  with 
5  c.c.  of  a  20  per  cent,  solution  of  phosphoric  acid,  and  distiUing 
nearly  to  dryness.  Benzoic  and  sulfurous  acids  distil,  and  the 
saccharin  remains  in  the  flask.  Sulfuric  acid  may  also  be  used. 
A  current  of  steam  through  the  distilKng  flask  is  more  efficient. 

Salicylic  acid.  This  is  usually  detected  by  extraction  with 
an  immiscible  solvent.  25  to  50  c.c.  of  the  sample  are  rendered 
feebly  acid  with  a  few  drops  of  sulfuric  acid  and  shaken  vigor- 
ously with  about  an  equal  bulk  of  a  mixture  of  equal  parts  of 
ether  and  petroleum  spirit,  the  liquids  are  allowed  to  separate, 
as  much  as  possible  of  the  solvent  is  drawn  off,  filtered,  and 
evaporated  at  a  gentle  heat.  When  salicylic  acid  has  been 
added  as  a  preservative,  distinct  needle-like  crystals  will  be 
usually  seen.  A  few  drops  of  water  should  be  added  and  then 
a  drop  of  very  dilute  ferric  chlorid  solution.  The  reaction  of 
salicylic  acid  is  distinct.  When  a  crystalline  deposit  cannot  be 
obtained,  a  larger  quantity  of  the  sample  may  be  concentrated 
at  a  gentle  heat  and  extracted  as  above.  (See  under  * 'Alcoholic 
Beverages.") 

Some  analysts  prefer  chloroform  as  the  extracting  liquid. 
In  this  case  the  shaking  should  be  done  in  a  stoppered  sepa- 
rator, that  the  solvent  may  be  readily  drawn.  A  solution  of 
ammonio-ferric  alum  is  in  some  respects  preferable  to  ferric 
chlorid  as  a  testing  agent.  If  50  c.c.  of  the  sample  properly 
extracted  does  not  give  a  visible  deposit  of  the  acid,  it  is  not 
likely  that  it  has  been  added  as  a  preservative. 

Saccharin,  A  suitable  amount  of  the  sample  (50  or  100 
c.c.)  is  acidified  with  dilute  (25  per  cent.)  sulfuric  acid  and 
extracted  with  a  mixture  of  equal  parts  of  petroleum  spirit 


PRESERVATIVES  8l 

boiling  below  60°  and  ether.  The  solvent  is  evaporated  at  a 
gentle  heat.  The  presence  of  saccharin  in  the  residue  may  be 
detected  by  the  taste.  2  c.c.  of  a  saturated  solution  of  sodium 
hydroxid  are  added  and  the  dish  heated  until  the  residue  dries 
and  then  to  210-215°,  and  maintained  thus  for  half  an  hour. 
The  saccharin  is  converted  into  salicyHc  acid,  which  may  be 
detected  in  the  residue  by  acidulating  it  with  sulfuric  acid  and 
applying  the  ferric  chlorid  test.  If  salicylic  acid  be  present 
originally  in  the  sample,  the  residue  from  the  petroleum  spirit 
and  ether  solution  is  dissolved  in  50  c.c.  of  dilute  hydrochloric 
acid,  bromin  water  added  in  excess,  the  liquid  shaken  well, 
and  filtered.  Sahcylic  acid  is  completely  removed  as  a  bromi- 
nated  derivative.  The  filtrate  is  made  strongly  alkaline  with 
sodium  hydroxid,  evaporated,  and  fused  as  described  above. 

A  substance  capable  of  giving  a  reaction  by  this  method  often 
exists  in  wine.  For  the  elimination  of  this  error,  see  under 
** Alcoholic  Beverages." 

Benzoic  acid  and  benzoaies.  Mohler's  method:  About 
100  grams  of  the  sample  are  made  alkaline  with  sodium  hydroxid 
and'  evaporated  to  a  paste,  which  is  then  acidified  with  hydro- 
chloric acid,  mixed  with  sand,  and  extracted  with  ether.  The 
ether  is  evaporated  spontaneously,  the  residue  moistened  with 
2  c.c.  of  sulfuric  acid,  heated  until  acid  vapors  escape  (at  about 
240°),  and  a  few  decigrams  of  sodium  nitrate  added  in  small 
portions,  until  the  liquid  becomes  colorless.  The  liquid  is 
poured  into  excess  of  ammonium  hydroxid  and  a  drop  of 
ammonium  sulfid  solution  added.  Benzoic  acid  is  indicated  by 
a  yellow,  changing  to  reddish-brown. 

Peter's  method:  The  material  is  made  slightly  acid  and  ex- 
tracted with  chloroform,  which  is  then  evaporated  sponta- 
neously. The  vessel  containing  the  residue  is  placed  in  melting 
ice,  2  c.c.  of  sulfuric  acid  added,  and  stirred  until  the  residue 
is  dissolved.  Barium  dioxid  is  dusted  into  the  mass,  with  con- 
stant stirring,  until  the  liquid  begins  to  foam,  when  3  c.c.  of 


82  FOOD   ANALYSIS 

hydrogen  dioxid  (3  per  cent.)  are  added  drop  by  drop.  The 
dish  is  then  removed  from  the  cold  bath,  the  contents  diluted 
with  water  to  convenient  bulk,  and  filtered.  The  acid  filtrate 
is  extracted  with  chloroform.  The  benzoic  acid  will  have  been 
converted  into  salicylic  acid  by  the  process  and  the  latter  may  be 
detected  by  dilute  solution  of  ferric  chlorid  or  ammonio-ferric 
sulfate. 

Boric  acid  and  borax.  These  may  be  detected  in  many 
food-articles,  especially  milk  and  milk  products,  by  the  follow- 
ing test:  A  few  drops  of  the  sample  or  of  a  solution  obtained 
by  shaking  some  of  it  in  water  are  mixed  with  a  drop  of  strong 
hydrochloric  acid  and  a  drop  of  strong  alcoholic  solution  of 
turmeric,  evaporated  to  dryness  at  a  gentle  heat,  and  a  drop 
of  ammonium  hydroxid  added  to  the  residue  when  cold.  A 
dull  green  stain  shows  that  boric  acid  is  present. 

Borates  being  normal  constituents  of  many  fruits,  quali- 
tative tests  are  not  sufficient  to  determine  if  the  preservative 
has  been  added.  For  methods  of  quantitative  determination, 
see  under  "Alcoholic  Beverages." 

Fluorids.  100  grams  of  the  sample  are  made  slightly  alka- 
line with  ammonium  carbonate,  heated  to  boiling,  a  few  centi- 
meters of  calcium  chlorid  solution  added,  and  heating  con- 
tinued for  5  minutes.  The  precipitate  is  collected,  washed, 
dried,  transferred  to  a  platinum  crucible,  and  ignited.  When 
the  mass  is  cold,  a  few  drops  of  strong  sulfuric  acid  are  added, 
and  the  crucible  covered  with  a  piece  of  glass  partly  protected 
on  the  lower  side  by  paraffin.  The  bottom  of  the  crucible  is 
then  heated  for  an  hour  at  a  temperature  between  75°  and  80°. 
The  glass  is  etched  if  fluorids  are  present. 

Borofluorids  and  silico fluorids.  200  grams  of  the  sample 
are  made  alkaline  with  calcium  hydroxid  solution,  .evaporated 
to  dryness,  incinerated,  and  the  ash  extracted  with  sufficient 
acetic  acid  to  decompose  carbonates.  The  residue  is  col- 
lected on  a  filter,  washed,  again  extracted  with  acetic  acid. 


PRESERVATIVES  83 

and  filtered.  The  filtrate  contains  any  boric  acid  that  may  be 
present  and  is  tested  for  this  substance  as  directed  on  page 
82.  The  insoluble  residue  contains  the  calcium  silicate  and 
calcium  fluroid.  The  filter  and  residue  are  ashed,  a  portion 
of  the  mass  mixed  with  a  little  precipitated  silica  and  2  c.c. 
of  sulfuric  acid,  and  placed  in  a  short  test-tube  to  which  is 
attached  a  small  U-tube  containing  a  few  drops  of  water. 
The  test-tube  is  heated  cautiously  in  a  water-bath;  any  sili- 
con fluorid  that  may  be  formed  from  fluorin  present  will  pro- 
duce a  gelatinous  deposit  in  the  U-tube.  If  boric  acid  has 
been  found  in  the  filtrate  noted  above,  it  may  be  assumed  that 
any  fluorin  is  in  the  form  of  borofluorid;  but  if  boric  acid  is 
not  present,  the  other  portion  of  the  ash  from  the  filter  and 
residue  is  treated  with  sulfuric  acid  without  previous  addition 
of  silica.  If  gelatinous  silicic  acid  be  formed,  the  compound 
was  originally  siHcofluorid. 

Formaldehyde.  The  tests  for  formaldehyde  have  been 
mostly  adapted  to  its  detection  in  milk. 

One  of  the  most  delicate  and  positive  reactions  of  formalde- 
hyde is  as  follows:  To  a  few  c.c.  of  the  suspected  liquid,  a 
pinch  of  phenylhydrazin  hydrochlorid  is  added,  the  liquid 
shaken  and  a  drop  of  a  dilute  solution  of  sodium  nitroprussid 
added  and  then  a  few  drops  of  sodium  hydroxid.  A  deep  blue 
color  is  at  once  produced  with  formaldehyde.  The  nitro- 
prussid solution  should  be  fresh.  The  test  is  applicable  to 
milk,  but  the  color  is  grayish-green. 

Another  test  is  the  addition  of  a  small  amount  of  a  solution  of 
I  per  cent,  of  phloroglucol  and  about  25  per  cent,  of  sodium 
hydroxid  in  water.  This  produces  a  rose-red.  The  test  is  best 
applied  by  running  the  test  solution  by  means  of  a  pipet  under 
the  suspected  liquid. 

Formaldehyde  may  be  obtained  pure  by  distillation  of  the 
sample,  especially  in  a  current  of  steam.  An  investigation  by 
Leonard,  H.  M.  Smith,  &  Richmond  showed  that  with  or- 


84  FOOD   ANALYSIS 

dinary  aqueous  solutions,  about  30  per  cent,  of  the  formalde- 
hyde has  passed  over  when  20  per  cent,  of  the  liquid  has  been 
distilled,  and  nearly  50  per  cent,  when  40  per  cent,  of  the  liquid 
has  been  distilled.  A  larger  proportion  distils  if  sulfuric  acid 
be  added  to  the  liquid.  For  details  of  this  and  for  other  tests 
for  formaldehyde,  see  under  ''Milk." 

Determination  oj  Formaldehyde.  B.  H.  Smith,^  who  also  in- 
vestigated the  methods  for  this  purpose,  finds  that  the  choice  will 
depend  on  the  strength  of  the  solution.  For  moderately  strong 
solutions  the  iodin  method  of  Romijn  is  satisfactory. 

10  c.c.  of  the  solution,  which  should  be  diluted  so  as  not  to 
contain  more  than  3  per  cent  of  formaldehyde,  are  mixed  with 
25  c.c.  ^  iodin  solution  and  sufficient  strong  sodium  hydroxid 
solution  added  to  make  the  liquid  bright  yellow.  After  stand- 
ing 10  minutes,  hydrochloric  acid  is  slowly  added  until  a 
marked  brown  liquid  is  produced.  The  iodin  is  then  titrated 
with  thiosulfate  in  the  usual  way.  The  amount  of  iodin  that 
has  been  taken  up,  multiplied  by  0.118,  will  give  the  amount  of 
formaldehyde.  A  blank  experiment  should  be  made  and  any 
necessary  correction  appHed. 

For  dilute  solutions,  the  potassium  cyanid  method  is  best. 

30  c.c.  of  ^  silver  nitrate  solution  are  acidulated  with  15  drops 
of  nitric  acid.  10  c.c.  of  this  solution  are  mixed  with  10  c.c.  of 
normal  potassium  cyanid  solution  (6.5  grams  in  1000  c.c),  then 
water  to  make  50  c.c,  the  liquid  shaken,  filtered  through  a  dry 
filter  and  25  c.c.  set  apart  for  titration  as  below  (Volhard's 
method). 

Another  10  c.c  of  cyanid  solution  are  mixed  with  a  measured 
amount  of  the  formaldehyde  solution  (which  must  not  contain 
more  than  0.03  gram  of  formaldehyde),  the  mixture  added  to 
another  10  c.c  of  the  acid  silver  nitrate  solution,  shaken,  made 
up  to  50  c.c,  filtered  and  25  c.c.  of  the  filtrate  taken  as  before. 
The  two  solutions  contain  excess  of  silver,  but  the  second  con- 
tains more,  because  the  formaldehyde  converts  the  cyanid  into 
a  compound  that  does  not  precipitate  silver. 


PRESERVATIVES  85 

Standard  thiocyanate  solution  is  prepared  by  dissolving  10 
grams  of  potassium  thiocyanate  (or  8  grams  of  ammonium 
thiocyanate)  in  water  to  make  1000  c.c.  The  solution  is  ap- 
proximately -7^.     Its  value  in  silver  must  be  determined  thus : 

50  c.c.  of  -7^  silver  nitrate  are  mixed  with  i  c.c.  of  nitric 
acid  and  i  c.c.  of  saturated  solution  of  ammonium  ferric  sul- 
fate, and  thiocyanate  solution  added  until  a  faint  permanent 
brown  is  produced. 

The  titration  of  the  acid  filtrates  is  conducted  in  the  same 
manner.  To  each  filtrate  is  added  i  c.c.  of  ferric  sulfate  and 
then  the  thiocyanate  until  the  faint  permanent  brown  is  ob- 
tained. If  the  thiocyanate  is  exactly  -^,  the  difference  in  c.c. 
required  for  the  two  filtrates  multiplied  by  0.006  will  give  the 
amount  of  formaldehyde  in  the  quantity  originally  taken. 
If  the  thiocyanate  is  not  -^  the  result  must  be  reduced  to  that 
basis. 

For  detection  of  sulfites  see  under  "Alcoholic  Beverages." 

13-naphthol.  Several  allied  antiseptics  of  this  type  may  be 
detected  by  the  following  method:  200  grams  of  the  sample 
are  acidified  with  sulfuric  acid  and  distilled  with  open  steam 
until  150  c.c.  of  distillate  are  obtained.  This  liquid  is  shaken 
with  20  c.c.  of  chloroform,  the  latter  withdrawn,  rendered 
alkaline  with  potassium  hydroxid,  and  heated  almost  to  boiling 
for  a  few  minutes.     Color  changes  as  follows : 

Salol, light  red. 

Phenol, light  red,  to  brown,  to  colorless. 

/?-naphthol, deep  blue,  to  green,  to  brown. 

A  portion  of  the  distillate  may  also  be  tested  as  follows :  2 5  c.c. 
are  made  faintly  alkaline  with  ammonium  hydroxid,  then 
faintly  acid  with  nitric  acid  and  then  a  drop  of  strong  sodium 
nitrite  solution.  /3-naphthol  develops  a  rose  red,  but  the  reaction 
is  sometimes  uncertain  and  seems  to  be  affected  by  light.  The 
so-called  hydronaphthol  gives  the  same  effect. 


86  FOOD   ANALYSIS 

Ahrastol  (Asaprol).  A  characteristic  reaction  for  abrastol  is 
that  described  by  Pintus'^ ;  the  yellow  produced  by  acid  mercuric 
nitrate  solution  prepared  as  directed  for  the  clarification  of  milk 
(see  under  Milk). 

It  can  be  extracted  from  jellies,  fruit  juices,  wines  and  similar 
articles  by  acidulation  with  dilute  sulfuric  acid  and  agitation 
with  ether,  petroleum  spirit,  chloroform  or  carbon  tetrachlorid. 
On  adding  to  the  immiscible  solvent  a  small  amount  of  mercuric 
nitrate  solution  and  shaking  the  liquids  for  a  few  seconds,  the 
watery  liquid  will  become  yellow,  rapidly  changing  to  bright 
red.^ 

The  following  method,  devised  by  Sinabaldi,  especially  for 
wine,  is  applicable  to  other  food-articles. 

50  c.c.  of  the  sample  are  made  alkaline  by  cautious  addition 
of  ammonium  hydroxid,  shaken  gently  for  two  minutes  with 
amyl  alcohol,  and  the  liquids  allowed  to  separate.  If  this  does 
not  occur  a  little  common  alcohol  should  be  added.  The  amyl 
alcohol  is  decanted,  filtered  if  turbid,  and  evaporated  to  dryness. 
The  residue  is  thoroughly  mixed  with  a  mixture  of  i  c.c.  of  nitric 
acid  and  i  c.c.  of  water,  heated  on  the  water-bath  until  half  of 
the  liquid  is  evaporated,  transferred  to  a  test-tube  by  the  aid 
of  I  c.c.  of  water,  0.2  gram  of  ferrous  sulfate  added  and  then 
ammonium  hydroxid  to  excess  with  constant  shaking.  If  the 
resulting  precipitate  is  reddish,  it  is  dissolved  in  a  few  drops  of 
sulfuric  acid  and  treated  with  ferrous  sulfate  and  ammonium 
hydroxid  as  before.  As  soon  as  a  dark  greenish  precipitate 
has  been  obtained,  it  is  dissolved  in  sulfuric  acid,  the  Hquid 
well  shaken  and  filtered.  In  the  absence  of  abrastol  the  filtrate 
is  light  yellow,  with  abrastol  in  appreciable  amount  it  is  red. 


SPECIAL  METHODS 

STARCH 
Detection. 

The  reaction  with  iodin  affords  a  delicate  method  for  detect- 
ing starch.  The  color  is  shown  by  undissolved  granules,  but 
it  is  more  satisfactory  to  dissolve  it  by  boiling  with  water, 
allowing  the  solution  to  cool  and  adding  the  iodin,  preferably  as 
potassium  iodid-iodin  solution  (p.  26).  If  the  proportion  of. 
starch  be  large,  an  almost  black  precipitate  will  be  formed. 
The  depth  of  color  will  be  some  indication  of  the  amount 
present,  but  exact  determinations  cannot  be  made  by  this 
method. 

In  the  undissolved  condition,  starch  may  be  recognized 
by  the  microscope  and  its  source  often  determined.  A  magnify- 
ing power  of  from  150  to  300  diameters  will  be  required.  The 
characteristics  of  the  granules  are  seen  more  vividly  by  mount- 
ing them  in  a  dense  medium  such  as  chloral  hydrate  solution  or 
glycerol  (p.  26)  and  arranging  the  reflecting  mirror  so  as  to 
throw  an  oblique  light  upon  the  object.  By  this  means  distinct 
markings,  termed  hilum  and  concentric  rings,  are  recognized. 
If  the  chloral-hydrate  iodin  solution  (p.  26)  be  employed  for 
mounting,  or  if  a  drop  of  the  potassium  iodid-iodin  solution  be 
introduced  under  the  cover  of  a  glycerol-  or  water-mounting, 
the  granules  will  become  blue. 

With  polarized  light,  many  starches  show  on  the  dark  field — 
i.  e.,  with  crossed  nicols — dark  bands  radiating  from  the  hilum, 
giving  the  appearance  of  a  Maltese  cross.  For  this  examina- 
tion the  object  is  mounted  uncolored  in  one  of  the  denser  media 
and  the  light  thrown  directly  from  below.     By  inserting  a  selenite 

87 


88  FOOD  ANALYSIS 

plate  between  the  object  and  the  lower  nicol,  colors  will  be 
produced  with  many  starches.  Muter  employed  a  selenite 
giving  a  green  field,  but  red  and  red- violet  fields  are  also  suitable. 
The  successful  application  of  these  methods  requires  good 
apparatus  and  considerable  practice.  A  careful  study  of  starch- 
granules  of  authentic  origin  should  always  be  made  before 
deciding  as  to  the  nature  of  any  specimen. 

The  size,  appearance  and  effect  on  polarized  light  may  be. 
much  altered  by  heating  starch,  and  possibly  by  some  other 
manufacturing  operations. 

A  synopsis  of  the  characters  of  the  principal  starches  is  pre- 
sented in  the  annexed  tables.  A  micron  (o.ooi  miUimeter) 
may  be  converted  into  thousandths  of  an  inch  by  multiplying 
by  0.03937.  The  factor  0.04  will  be  near  enough  for  most 
cases.  The  classification  is  essentially  that  of  Muter,  the  basis 
being  the  predominating  form  of  the  granule,  the  distinctness 
and  position  of  the  hilum  and  markings,  the  appearance  under 
polarized  Hght,  with  or  without  selenite  plate.  Muter  indi- 
cated five  groups,  each  group  designated  by  the  name  of  an 
important  type  of  starch,  as  follows : 

Potato  Group. — Oval  or  ovate  granules,  showing  hilum 
and  concentric  rings  clearly,  cross  and  colors  usually  distinct. 

Legume  Group. — Round  or  oval  granules,  hilum  marked, 
rings  faint,  but  rendered  visible  in  cases  by  chromic  acid  solu- 
tion, cross  and  colors  feeble. 

Wheat  Group. — Round  or  oval  granules,  hilum  and  rings 
generally  invisible,  feebly-marked  cross  and  colors. 

Sago  Group. — ^Truncated  granules,  hilum  distinct,  faint 
rings,  cross  and  colors  fairly  marked. 

Rice  Group. — Polygonal  granules,  hilum  distinct,  rings 
faint,  cross  and  colors  usually  faint. 

In  the  description  of  individual  starches,  the  term  "eccen- 
tric" denotes  that  the  hilum  is  not  in  the  apparent  center  of 
the  granule.     The  granule  is  often  described  as  oval,  circular 


STARCH 


89 


or  polygonal,  terms  which  are  strictly  applicable  to  surfaces. 
It  will  be  understood,  therefore,  that  such  terms  refer  to  the 
apparent  cross-section  of  the  granule  as  it  is  usually  viewed. 
The  dimensions  given  must  be  regarded  as  the  most  frequent; 
granules  not  included  within  the  limits  will  often  be  found. 
Polarized  hght  is  affected  to  some  extent  by  almost  all  starch 
granules,  if  very  close  observation  is  made. 


Source. 

Size  in 
Microns. 

Potato, 

60-100 

Canna, 

45-135 

Maranta,   

10-70 

Natal     arrow- 

root,   

35-40 
30-60 

Turmeric, 

Ginger, 

40 

Mother-cloves, 

20-60 

Banana, 

40-80 

General  Character 
or  Granules. 


Smaller  granules  round, 
large  ones  ovate;  hi- 
lum  a  spot,  eccentric; 
rings  numerous  and 
complete. 

Irregular  ovate;  hilum 
annular,  eccentric; 
rings  incomplete, 
narrow  and  regular. 

Ovate;  hilum  eccen- 
tric, circular  or  linear, 
often  cracked;  rings 
numerous,  not  very 
distinct;  sometimes  a 
projection  at  one  end. 

Ovate  to  circular,  ir- 
regular projections; 
hilum  eccentric, 
cracked;  rings  dis- 
tinct. 

Ovate,  often  much  nar- 
rowed at  one  end; 
hilum  eccentric,  dot- 
like;   rings  indistinct. 

Ovate,  many  with  a 
projection  on  one  end; 
hilum  and  rings 
scarcely  visible. 

Ovate;  hilum  a  dis- 
tinct spot,  eccentric; 
rings  visible. 

Ovate  but  often  very 
narrow  in  proportion 
to  length;  hilum  a 
spot,  eccentric;  rings 
distinct. 


With  Polarizer. 


Without  Selenite. 


Well-marked 
.     cross. 


Well-marked 
cross. 

Well-marked 
cross. 


Well-marked 
cross. 


Well-marked 
cross. 


Faint 


Well-marked 
cross. 

Faint  cross. 


With   Selenite. 


Well-marked 
colors. 


Well-marked 
colors. 


Well-marked 
colors. 


Well-marked 
colors. 


Well-marked 
colors. 


Faint  colors. 


Well-marked 
colors. 

Faint  colors. 


go 


FOOD  ANALYSIS 


With  Polarizer. 

Size  in 
Microns. 

General  Character 
OF  Granules. 

Source. 

Without  Selenite. 

With  Selenite. 

Bean, 

3S 

Reniform      or      ovate; 

Cross  indis- 

Colors very 

hilum  stellate  or  fur- 

tinct. 

faint. 

row-like;      rings   very 

faint. 

Pea, 

15-30 

Reniform  or  ovate;   hi- 
lum elongated;    rings 

Cross  indis- 
tinct. 

Colors  very 
faint. 

very  faint. 

Lentil, 

30 

Reniform      or      ovate ; 

Cross  indis- 

Colors very 

hilum  elongated,   dis- 

tinct. 

faint. 

tinct;  rings  visible. 

Nutmeg, 

5-50 

Rounded,    collected   in 
groups  of  two  to  four; 
lilum    stellate;     rings 
invisible. 

Cross  faint. 

Colors  very 
faint. 

Wheat, 

2-50 

Mostly  roundish,  chief- 

Cross not  well 

Colors  very 

ly    the    smallest    and 

marked. 

faint. 

largest   sizes    present; 

hilum  indistinct,  near- 

ly  central;     rings   in- 

distinct. 

Barley, 

15-40 

Resembles    wheat    but 

Cross  not  well 

Colors  very 

some  granules  slightly 

marked. 

faint. 

angular    or    elliptical; 

rings     more     distinct 

than  wheat. 

Rve 

20-60 

Resembles   wheat;    hi- 
lum distinct,   stellate; 

Cross  not  well 
marked. 

Colors  verv 

^^j  ^> 

faint. 

rings    often     visible. 

Distorted    forms    not 

infrequently  occur. 

Dhoura, 

1-3 

Round,  hilum  faint. 

Cross. 

Colors. 

12-33 

Round;   no  hilum. 

Cross   faint. 

Colors  faint. 

Acorn, 

20 

Round    or    nearly    so; 

Cross  not  well 

Colors   not 

hilum  eccentric. 

marked. 

well 
marked. 

Cacao, 

5-10 

Round;      hilum      and 

Cross  not  well 

Colors  not 

rings  indistinct. 

marked. 

well 
marked. 

Saffo, 

25-66 

Ovate,    truncated;     hi- 
lum a  circle  or  spot; 

Well-marked 
cross. 

Well-marked 

KJCVgW, 

colors. 

rings  faint. 

Prepared  sago. 

Characters  less  distinct 
than  in  raw  sago. 

Tapioca, 

8-22 

Circular;    hilum  a  slit, 

Well-marked 

Well-marked 

nearly  central. 

cross. 

colors. 

Prepared  tapi- 

oca,   

Characters  less  distinct 
than  in  raw  form. 

STARCH 


91 


With  Polarizer. 

Source. 

Size  in 

General  Character 

Microns. 

OF  Granules. 

Without  Selenite. 

With  Selenite. 

Cinnamon, 

8-20 

Truncated  at  one  end, 

Well-marked 

Well-marked 

two   to   four  granules 

cross. 

colors. 

often    joined;     hilum 

distinct,    nearly    cen- 

tral; rings  invisible 

Rice, 

5-10 

Pentagonal,  hexagonal, 
occasionally     triangu- 

Cross distinct. 

Colors    dis- 

well marked. 

tinct. 

lar  with  sharp  angles; 

hilum    distinct    under 

high  power. 

Buckwheat, . . . 

5-20 

Polygonal,      angles 

Cross     d  i  s  - 

Colors     dis- 

somewhat     rounded; 

tinct. 

tinct. 

hilum  central,  spot  or 

star;      granules    often 

compound. 

Oat, 

5-30 

Mostly     polygonal,     a 
few  spherical;    hilum 

Faint  cross. 

Faint  colors. 

and  rings  visible  only 

with       high       power; 

often  compound. 

Maize, 

5-20 

Round     to     polygonal, 
angles  usua  ly  round- 
ed;      hilum     central; 
crack   or  star;     rings 
nearly  invisible. 

Faint  cross. 

Faint  colors. 

Pepper, 

0-5 -5 

Polygonal,   very  small. 

Cross  with 

Color     with 

sometimes        showing 

high  power. 

high  power. 

Brownian    movement, 

sometimes  united  into 

large  irregular  masses; 

hilum  only  seen  with 

high  power. 

According  to  Lintner*  potato-starch  becomes  pasty  suddenly 
at  62-64°;  cereal  starches  become  pasty  gradually  at  from 
80-85°.  Diastase  acts  on  ungelatinized  cereal  starches  at 
comparatively  low  temperatures ;  ungelatinized  potato-starch  is 
hydrolyzed  only  at  a  comparatively  high  temperature. 


Barley. 


Pea. 


Potato. 


Oat. 


Maize. 


Rice. 


Bean. 


Wheat. 


Rye. 


Arrowroot. 


Buckwheat. 


92 


STARCH  93 

Determination. 

The  exact  quantitative  determination  of  starch  is  difficult. 
The  proposed  methods  have  been  carefully  investigated  by 
Wiley  &  Krug,  who  have  shown  that  in  the  presence  of  vegetable 
tissue  containing  pentosans  or  similar  carbohydrates  the  diastase 
method  is  alone  trustworthy.  The  first  method  is  applicable 
to  assaying  commercial  starches. 

Hydrochloric  Acid  Method. — ^3  grams  of  the  substance 
are  treated  with  about  50  c.c.  of  cold  water  for  an  hour,  with 
frequent  stirring ;  the  residue  is  collected  on  a  filter  and  washed 
with  sufficient  water  to  make  a  total  of  250  c.c.  This  Hquid 
contains  the  soluble  carbohydrates.  The  undissolved  residue 
is  heated  for  2J  hours  with  2.5  per  cent,  hydrochloric  acid  (200 
c.c.  water  and  20  c.c.  hydrochloric  acid,  sp.  gr.  1.125)  in  a  flask 
provided  with  an  inverted  condenser,  cooled,  neutralized  with 
sodium  carbonate,  made  up  to  250  c.c,  filtered,  and  the  dextrose 
determined  in  an  aliquot  portion  of  the  filtrate.  The  weight 
of  dextrose  multiphed  by  0.9  gives  the  weight  of  starch. 

Diastase  Method. — 3  grams  of  the  finely-powdered  sub- 
stance are  extracted  on  a  hardened  filter  with  five  successive 
portions  of  10  c.c.  of  ether,  washed  with  150  c.c.  of  a  10  per 
cent,  alcohol,  and  then  with  a  little  strong  alcohol.  The 
residue  is  mixed  in  a  beaker  with  50  c.c.  of  water.  The  beaker 
is  immersed  in  boihng  water,  the  contents  stirred  constantly 
until  all  the  starch  is  gelatinized,  cooled  to  55°,  and  20  c.c.  of 
malt-extract  added.  The  liquid  is  maintained  at  55°  for  i 
hour,  heated  again,  boihng  for  a  few  minutes,  cooled  to  55°,  20 
c.c.  of  malt-extract  added  and  maintained  at  55°  until  a  micro- 
scopic examination  of  the  residue  shows  no  starch  with  iodin. 
It  is  cooled  and  made  up  directly  to  250  c.c.  and  filtered.  200 
c.c.  of  the  filtrate  are  placed  in  a  flask  with  20  c.c.  of  a  25  per 
cent,  solution  of  hydrochloric  acid  (sp.  gr.  1.125),  connected  with 
a  reflux  condenser,  and  heated  in  boiling  water  for  2  J  hours.     It 


94  FOOD   ANALYSIS 

is  nearly  neutralized,  while  hot,  with  sodium  carbonate,  made  up 
to  500  c.c,  mixed,  poured  through  a  dry  filter,  and  the  dextrose 
determined  in  an  aliquot  part.  Calculate  the  dextrose  to  starch 
by  multiplying  by  0.9. 

Preparation  of  Malt  Extract. — 10  grams  of  fresh,  finely 
ground  malt  are  macerated  overnight  at  about  25°  with  200  c.c. 
of  water,  filtered,  the  amount  of  dextrose  in  a  given  quantity  of 
the  filtrate  after  boihng  with  acid  determined  as  in  the  starch 
determination,  and  the  proper  correction  noted.  If  diastase - 
be  used,  a  correction  will  be  unnecessary.  A  good  diastase 
is  now  easily  obtainable.  Commercial  malt  extracts  are  liable 
to  be  destitute  of  diastatic  power. 

In  the  application  of  the  diastatic  method,  the  material 
must  be  ground  very  fine  and  the  preHminary  extraction  with 
ether  must  not  be  omitted.  In  many  cases  it  will  be  more 
convenient  to  make  the  extraction  in  the  continuous  extractor. 
If  a  large  tube  is  used,  several  samples  may  be  treated  at  once 
by  tying  each  in  filter-paper.  The  centrifugal  apparatus  may 
also  be  used.  The  fine  material  is  shaken  up  with  ether  in  the 
proper  tubes,  whirled  for  a  short  time,  the  ether  poured  off, 
fresh  ether  added  and  again  whirled,  and  the  operation  repeated 
until  the  necessary  amount  of  solvent  has  been  used.  The 
Hquid  may  be  poured  off  closely  each  time.  Extraction  with 
carbon  tetrachlorid  may  be  better,  but  the  result  may  not  be 
equivalent  to  that  with  ether. 

FLOURS   AND   MEALS 

Meal  is  coarsely  ground,  flour  is  finely  ground  material. 
Most  of  the  forms  used  as  foods  are  derived  from  plants  be- 
longing to  the  order  Graminece,  but  buckwheat,  banana,  and 
potato  are  not  of  this  order.  The  distinction  between  the 
different  flours  and  meals  is  based  in  part  on  the  microscopic 
characters  of  the  starches  as  indicated  under  that  head,  but 
chemical  tests  are  in  some  cases  available. 


STARCH  95 

The  commercial  value  of  wheat  flour  depends  upon  its 
color  and  texture  and  upon  quantity  and  quality  of  gluten. 
The  latter  differs  much  in  different  varieties  and  in  the  same 
variety  grown  in  different  localities.  In  whole-wheat  flour 
containing  about  lo  per  cent,  of  gluten  the  quantities  of  the 
chief  proteids  are  about  as  follows : 

Globulin, 0.70 

Albumin, 0.40 

Proteose, 0.30 

Gliadin, 4.25 

Glutenin, 4.35 

Good  wheat  flour  will  yield  from  20  to  40  per  cent,  moist 
gluten  and  10  to  18  per  cent,  gluten  dried  at  100°.  Rye  flour 
contains  gliadin,  but  no  glutenin. 

COMPOSITION  OF  CEREAL  GRAINS 

Car- 
bohy- 
drates 
Weight  other 

OF  100  THAN 

Kernels    Moist-  6.25  Ether  Crude  Crude 

IN  Grams,     uke.  N.  Extract,  Fiber.  Ash.     Fiber. 
Typical    u  n  h  u  1 1  e  d 

barley, 10.85  ii.o  2.25  385  2.5           69.55 

Typical  American 
maize, 38.0  10.75  lo.o  4.25  1.75  1.5  71-75 

Typical  wheat,  .   .   .  3.85  10.6  12.25  1-75  2.4  1.75  71.25 

Sweet  corn,  19  sam- 
ples (Richardson),  8.44  11.48  8.57  2.82  1.97  66.72 

Typical  American 
buckwheat 3.0  12.0  10.75  2.0  10.75  1.75  62  75 

Typical  rye 2.5  10.5  12.25  i-5  2.1  1.9  71.75 

Typical  unhulled 
oats, 30  100  12.0  4.5  12.0  3.4  58.0 

Typical  rice,  un- 
hulled   3.0  10.5  7.5  1.6  9.0  4.0  67.4 

Typical  rice,  hulled, 
but  unpolished,  .   .  2.5  12.0  8.0  2.0  i.o  i.o  76.0 

Typical  rice,  pol- 
ished,    2.2  12.4  7.5  0.4  0.4  0.5  78.8 

Typical  rye 2.5  10.5  12.25  i-5  2.1  1.9  71.7 

Typical  wheat,  .   .  .  3.85  10.6  12.25  1.75  2.4  1.75  7«-25 


A  detailed  description  of  the  proteid  and  other  constituents 
of  cereal  grains  has  been  published  by  the  United  States  De- 


96  FOOD  ANALYSIS 

partment  of  Agriculture.  The  table  on  page  95  has  been  taken 
from  this.  The  proteids  are  calculated  by  multiplying  the 
nitrogen  by  the  factor  6.25,  but  the  investigations  by  Osborne, 
Chittenden,  and  Voorhees  indicate  that  the  following  factors 
would  be  better:  Maize,  6.23;  barley,  rye,  and  wheat,  each 
5.68;  oats,  6.10.  A  recalculation  of  the  proteids  by  corrected 
factors  will  change  the  proportions  of  the  carbohydrates,  since 
these  were  determined  by  difference. 

Wheat  Flour. — Good  wheat  flour  is  a  fine  white  powder 
with  a  very  faint  yellow  tinge.  Several  tests  are  recognized 
for  its  examination,  among  which  are  the  following : 

Color  Test. — The  sample  may  be  compared  with  one  of 
known  quality  by  laying  out  heaps  of  equal  size,  say,  3  cm. 
by  8  cm.,  and  0.5  cm.  deep.  If  this  be  done  on  a  colorless 
glass  plate,  the  examination  may  be  made  with  both  white 
and  colored  background,  and  the  plate  may  subsequently  be 
immersed  in  water  (not  over  35°)  so  that  the  colors  produced 
on  wetting  may  also  be  observed. 

Doughing  Test. — This  consists  in  making  a  dough  with  15 
grams  of  the  sample  and  10  c.c.  of  water  and  comparing  color, 
firmness,  elasticity,  and  compactness. 

Gluten  Test. — 10  grams  of  the  sample  are  mixed  with  suf- 
ficient water  to  make  a  stiff  dough  and  allowed  to  stand  for 
one  hour.  The  mass  is  kneaded  in  a  piece  of  linen  in  running 
water  until  the  washings  are  clear.  The  fresh  gluten  thus 
obtained  should  have  a  faint  yellow  tinge,  be  tough  and  of 
such  consistency  that  it  can  be  pulled  out  into  threads.  Gray 
and  red  glutens  indicate  inferior  samples.  Good  gluten  swells 
at  150°  and  assumes  the  appearance  of  bread. 

Adulterations. — Flour  may  be  mixed  with  mineral  matters 
to  increase  weight,  with  alum  or  copper  sulfate  to  improve 
its  appearance,  or  with  cheaper  flours  or  starches.  It  may  also 
contain  seeds  of  weeds,  may  be  damp  or  decomposed,  or  may 
contain  fungi. 


STARCH 


97 


In  examining  for  these  adulterations,  determintions  of  ash, 
crude  fiber,  ether  extract,  and  total  nitrogen  are  of  consider- 
able value.  The  following  table  gives  some  data  on  these 
points,  but  the  limits  must  not  be  rigidly  interpreted.  The 
figures,  except  the  first  column,  have  been  calculated  on  the 
water- free  substance: 


COMPOSITION   OF   FLOURS 


Wheat,  .  .  . 

Rye 

Barley,   .   .    . 
Buckwheat, 

Rice 

Oat  (meal), 
Maize  (meal), 
Graham,    .   . 


Moisture. 


Max.    Mill, 


150 
J4.0 
150 
18.0 
15.0 
10.0 
18.0 
150 


9.0 
12.0 

lO.O 

12.5 

lO.O 

6.0 
8.0 
1 1.0 


Ash. 


Max.    Min. 


0.3 
0.5 
1.0 
0.8 
0.3 
2.0 
i.o 
1.8 


6.25  N. 


Max.    Min. 


15.0 
1 1.0 
12.0 
9-5 
lo.o 
18.0 
"•5 
1.5.0 


8.0 
6.0 
8.5 
.SO 
7.0 
14.0 
8.0 

lO.O 


Fiber. 


Ether 
Extract. 


Max.    Min.iMax.    Min 


1.0 
0.6 
0.6 
0.6 
0.4 
1-4 
3.5 
2.4 


0.1      2.0 


0.4 
0.3 
0.3 
0.1 
0.7 

0.7 
2.0 


1.0 
2.0 
2.0 
0.6 
9-5 
6.0 
2.2 


05 
0.9 
0.5 
0.8 
0.3 
6.5 
2.5 
1-9 


N-FREE 
EXIRACT. 


Max.    Min. 


82.0 
88.0 
87.0 
84.0 
85.0 
72.0 
63.0 
70,0 


Alum. 

Logwood  Method. — An  alkaline  solution  of  logwood  is  pre- 
pared as  follows :  Half  a  gram  of  fine  logwood  chips,  preferably 
freshly  cut  from  the  log,  is  macerated  for  10  hours  in  15  c.c.  of 
alcohol;  10  c.c.  of  the  solution  are  poured  off  and  mixed  with 
150  c.c.  of  water  and  10  c.c.  of  a  saturated  solution  of  am- 
monium carbonate.  To  make  the  test,  50  grams  of  the  flour 
are  made  into  a  thin  paste  with  water,  a  few  drops  of  the  log- 
wood solution  (freshly  prepared)  added,  and  the  mixture 
allowed  to  stand  several  hours.  Alum  produces  a  lavender- 
blue  lake. 

Chloroform  Method. — 200  grams  of  flour  are  shaken  in  a 
separatory  funnel  with  a  sufficient  amount  of  chloroform, 
allowed  to  stand  overnight,  and  the  materials  which  subside 
carefully  removed  through  the  stopcock.  This  material  may 
be  further  purified  by  shaking  a  second  time  with  a  little  chlo- 
roform and  then  transferred  to  a  watch-glass  and  the  chloro- 
form evaporated.     The  residue  is  treated  with  water,  the  solu- 


98  FOOD   ANALYSIS 

tion  separated  from  the  insoluble  portion  and  allowed 
to  evaporate,  when  the  crystals  of  alum  will  be  observed. 
The  crystals  may  be  dissolved  in  water  and  tested  for  sul- 
fates, aluminum,  potassium,  and  ammonium.  The  residue 
insoluble  in  water  should  be  examined  under  the  microscope 
for  mineral  matters.  The  steps  in  the  treatment  of  the 
residue  insoluble  in  chloroform  will  be  assisted  by  the  use  of  a 
centrifuge. 

Copper  sulfate  can  be  detected  by  the  ferrocyanid  method  as 
described  under  Bread. 

Ergot  in  Rye  Flour. — A  preliminary  test  may  be  made  to 
determine  if  the  flour  has  been  damaged  by  fungi.  Vogel 
advises  that  the  sample  be  stained  with  anilin  violet  and  exam- 
ined with  the  microscope.  Any  starch  granules  that  have 
been  injured  by  fungus  will  be  deeply  stained. 

Gruher^s  test:  A  little  of  the  flour  is  moistened  with  water 
on  a  microscope-slide,  a  cover- glass  placed  on,  and  the  mass 
heated  to  the  boiling-point  on  a  hot  plate  or  water-bath.  After 
cooling  it  is  examined  with  a  power  of  120  diameters.  Ergot 
will  be  recognized  by  its  high  refracting  power,  furrows,  and 
color-7-deep  violet  on  the  edge,  greenish-yellow  within.  A 
second  examination  with  a  power  of  about  300  diameters  will 
enable  any  doubtful  particles  to  be  recognized. 

Chemical  Tests. — 200  grams  of  the  sample  are  digested  with 
boiling  alcohol  as  long  as  any  color  is  extracted.  The  solu- 
tion is  treated  with  i  c.c.  of  sulfuric  acid  (1:3).  In  the  presence 
of  ergot  the  solution  will  be  red,  and  if  it  be  diluted  with  a  large 
volume  of  water,  the  color  may  be  extracted  from  separate 
portions  by  means  of  chloroform,  ether,  petroleum  spirit,  or 
amyl  alcohol. 

10  grams  of  the  sample  are  macerated  for  about  30  minutes 
with  a  mixture  of  20  c.c.  of  ether  and  10  drops  of  dilute  sulfuric 
acid  (i  :  5);  the  liquid  filtered,  washed  with  ether  until  the 
filtrate  amounts  to  15  c.c.     This  is  shaken  with  5  drops  of  a 


^  STARCH  99 

saturated  solution  of  sodium  bicarbonate.  The  chlorophyl 
remains  in  the  ether;  the  sodium  bicarbonate  solution  remains 
clear  if  the  flour  be  from  sound  grain,  but  takes  on  a  deep 
violet  color  if  ergot  be  present. 

Mixed  Flours. — The  following  data  are  taken,  with  but  few 
changes,  from  the  contributions  of  Bigelow  &  Sweetser  and 
Kraemer: 

Gluten  obtained  from  a  mixture  of  wheat  and  rye  flours  is 
dark  and  viscous,  without  homogeneity;  from  a  mixture  of 
wheat  and  barley  flours,  dark,  non-viscous,  and  dirty  reddish- 
brown;  from  a  mixture  of  wheat  and  oats,  dark  yellow;  from 
a  mixture  of  wheat  and  maize,  yellowish  and  non-elastic; 
from  a  mixture  of  wheat  and  leguminous  flour  it  varies  from 
a  grayish-red,  in  the  case  of  vetch  or  beans,  to  green,  in  the 
case  of  peas,  and  has  the  characteristic  odor  and  taste  of 
leguminous  products.  The  ash  of  leguminous  flour  is  deli- 
quescent, high  in  chlorids,  and  turns  turmeric  paper  brown; 
cereal  ash  is  the  reverse.  The  aqueous  extract  of  the  legu- 
minous flour  is  acid;  that  of  cereal  flour  is  faintly  alkaHne. 
If  the  filtrate  from  the  gluten  determination  of  flour  contain- 
ing leguminous  flour  be  made  alkahne  with  ammoniurji  hy- 
droxid,  allowed  to  stand  overnight,  and  the  clear  liquid  de- 
canted, dilute  sulfuric  acid  will  precipitate  legumin. 

For  the  detection  of  potato  flour  a  portion  of  the  sample  is 
rubbed  in  a  mortar  until  a  stiff  paste  is  obtained,  thinned  with 
more  water,  filtered,  and  the  clear  filtrate  tested  with  a  drop  of 
a  dilute  solution  of  iodin.  Potato  flour  produces  a  deep  blue, 
while  with  pure  wheat  flour  the  result  is  yellow  or  light  orange. 
If  a  mixture  of  cereal  and  potato  flours  be  dried,  spread  in  a  thin 
layer  on  a  glazed  black  surface,  and  examined  with  a  lens,  the 
potato  is  indicated  by  bright  and  glassy  particles  in  the  other- 
wise dull  white  substance. 

Vogel  extracts  the  flour  with  70  per  cent,  of  alcohol,  to 
which  5  per  cent,  of  hydrochloric  acid  has  been  added.     The 


lOO  FOOD   ANALYSIS 

extract  is  colorless  if  the  flour  consist  only  of  wheat  or  rye,  pale 
yellow  if  adulterated  with  barley  or  oats,  orange  yellow  with  pea 
flour,  purple  red  if  made  from  mildewed  wheat,  and  blood  red 
if  made  from  ergotized  wheat. 

Rice  in  Buckwheat  Flour. — When  pure  buckwheat  is  mixed 
with  water  into  a  thin  paste,  the  addition  of  calcium  hydroxid 
produces  a  dark  green,  which  becomes  red  when  acidified  with 
hydrochloric  acid.  Rice  flour  gives  a  yellow  color  with  potas- 
sium hydroxid  and  white  with  hydrochloric  acid.  A  mixture 
of  buckwheat  and  rice  flours  made  into  paste  is  changed  to  a 
light  green  color  by  potassium  hydroxid  and  becomes  flesh- 
colored  when  acidified  with  hydrochloric  acid. 

Wheat  in  Rye  Flour. — Kleeburg  has  advised  the  follow- 
ing test:  A  pinch  of  the  sample  is  mixed  on  a  small  glass 
plate  (a  microscope-slide  will  serve)  with  water  at  about  45° 
in  suflicient  quantity  that  the  particles  of  flour  still  float.  The 
mixture  is  spread  over  a  considerable  part  of  the  glass  and  a 
similar  glass  laid  upon  it  so  that  about  one-fourth  of  each 
glass  protrudes  at  the  ends.  The  two  glasses  are  pressed 
together,  the  exuded  liquid  wiped  off,  and  the  glasses  rubbed 
on  e^ch  other  several  times.  If  wheat  flour  be  present,  white 
spots  will  be  observed,  which  will  form  threads  on  being  rolled ; 
these  are  short  and  thin  if  the  proportion  of  wheat  be  small, 
and  thicker  and  longer  with  larger  amounts.  An  admixture 
of  5  per  cent,  of  wheat  flour  with  rye  is  said  to  be  thus  recogniz- 
able. 

Maize  in  Wheat  Flour. — Kraemer  has  devised  the  follow- 
ing test,  which,  he  states,  will  detect  5  per  cent,  of  maize  in 
wheat  flour:  i  gram  of  the  sample  is  mixed  with  15  c.c.  of 
good  glycerol  and  heated  to  boiling  for  a  few  minutes.  An 
odor  recalling  that  of  popcorn  indicates  maize. 

It  is  alleged  that  cheap  flours  have  been  adulterated  with 
sawdust.  G.  A.  LeRoy  applied  the  following  test  for  detect- 
ing this  addition:    A  small  amount  of  the  sample  is  gently 


STARCH  lOI 

warmed  with  the  acid  solution  of  phloroglucol  (page  26). 
Ordinary  wood-fiber  quickly  acquires  a  bright  red  tint,  while 
bran  particles  are  but  slightly  affected. 

BREAD 

Bread  is  made  by  baking  the  mass  obtained  by  kneading 
flour  with  water.  This  gives  the  so-called  unleavened  bread, 
but  it  is  usual  to  add  a  little  common  salt  to  the  water  and 
make  the  dough  light  by  inflating  it  with  carbon  dioxid.  This 
may  be  done  by  the  use  of  baking  powder,  or  by  mixing  the 
flour  with  water  containing  carbonic  acid  under  pressure  (aer- 
ated bread),  but  commonly  yeast  is  added  to  the  dough  and  the 
mixture,  called  the  ** sponge,"  allowed  to  stand  for  some  hours 
and  then  baked.  The  slight  fermentation  which  occurs  liber- 
ates carbon  dioxid. 

The  chemical  composition  of  bread  is  approximately  that  of 
the  flour  from  which  it  is  made.  The  moisture  usually  ranges 
from  30  to  40  per  cent.,  and  will  depend,  among  other  condi- 
tions, upon  the  quantity  and  quality  of  the  gluten,  and  the 
size  and  shape  of  the  loaf.  On  the  size  and  shape  will  also 
depend  the  relative  proportion  of  crust  to  crumb,  the  latter 
containing  about  twice  as  much  moisture  as  the  former.  The 
addition  of  potato  flour  or  rice  flour  will  enable  a  bread  to  be 
prepared  containing  a  much  larger  proportion  of  water  than 
usual.  The  addition  of  about  i  per  cent,  of  mashed  potatoes 
to  the  dough  is  said  to  render  the  bread  white  without  any 
notable  increase  in  the  amount  of  moisture  retained. 

The  proportion  of  fat  in  bread,  as  determined  by  the  ether 
extract,  is  apt  to  be  less  than  that  of  the  original  flour,  owing 
to  decomposition  of  the  fat  in  the  crust,  by  heat,  and  also  to 
the  inclosure  of  the  fat  particles  in  such  a  way  as  to  render 
them  difficult  of  extraction.  On  the  other  hand,  the  propor- 
tion of  fatty  matter  may  be  increased  by  the  use  of  milk  or  by 
the  material  used  to  grease  the  pans. 


102 


FOOD   ANALYSIS 


When  bread  is  raised  by  yeast,  some  solid  matter  is  lost  by  the 
fermentation.  According  to  Lawes  and  Gilbert,  this  is  prob- 
ably less  than  J  of  i  per  cent.,  and  appears  to  be  due  to  the 
decomposition  of  the  sugar.  The  unchanged  starch  is  not 
appreciably  altered  during  the  short  time  that  the  yeast  acts. 
The  ash  of  bread  will  be  higher  than  that  of  the  flour  if  salt 
or  baking  powder  has  been  added. 


Orig- 
inal 
Sub- 
stance 


Moist- 
ure. 


Vienna,  average  of  lo  sam- 
ples,       

Home-made,  average  of  2 
samples, 

Graham,  average  of  9  sam- 
ples, .         

Rye,  average  of  7  samples, 

Quaker,  average  of  3  sam- 
ples,       

Miscellaneous,  average  of 
9  samples,    .  ... 


38.71 
3302 

34-8 
3342 

36.16 
3441 


Pio- 
teids, 
NX 
5- 70. 


10.8 


2.51 

;i.86 


10.59 


In  the  Dry  Substance. 


Ether 
Ex- 
tract. 

Crude 
Fiber. 

Ash. 

Salt. 

1-73 
2.91 

1.02 

2.21 

0.97 

0.36 

1.74 
095 

0.41 
0.46 

1-95 

1-55 

2.29 
2.79 

1.68 
1-53 

0-93 
0.84 

1.07 
1-5 

0.92 
0.76 

Carbo- 

drates, 
exclud- 
ing 
Fiber. 


83.1 
84.75 

82.06 
84.36 

85.41 
85.66 


The  table  represents  the  average  composition  of  various 
breads  of  commerce  according  to  analyses  published  by  the 
Department  of  Agriculture.  The  loaves  weighed  approximately 
one  pound  each.     Trade  names  are  given  in  most  cases. 

Adulterations. — These  may  consist  in  the  use  of  damaged 
flour,  of  flours  other  than  that  purporting  to  be  present,  presence 
of  excess  of  water,  or  addition  of  alum  or  copper  sulfate  to 
improve  appearance. 

Alum.^Th^  bread  is  moistened  with  water  and  then  with 
some  of  the  alkaline  logwood  solution  (see  p.  97).     If  alum  be 


STARCH  103 

present,  the  bread  will  become  lavender-blue  in  an  hour  or 
two.  Pure  bread  assumes  a  light  red-brown  tint.  The  blue 
color,  however,  is  not  proof  of  the  presence  of  alum  unless 
it  is  permanent  at  the  temperature  of  boiling  water. 

Blyth  gives  the  following  test:  150  grams  of  the  material 
are  macerated  for  two  days  in  2  liters  of  water.  The-  solution 
is  strained  through  muslin  and  evaporated  at  a  gentle  heat  to 
small  volume;  a  strip  of  gelatin  immersed  in  this  liquid,  and 
then  in  the  alkaline  logwood  solution,  will  acquire  the  lavender 
color  if  alum  is  present  to  the  extent  of  0.03  per  cent. 

These  tests  are  not  applicable  to  sour  bread.  Vander- 
planken  recommends  the  following  modification  to  meet  the 
difficulty:  15  grams  of  the  sample  are  triturated  to  a  paste 
with  water  and  some  pure  sodium  chlorid  and  10  drops  of 
a  freshly-prepared  solution  of  logwood  in  alcohol,  and  then 
5  grams  of  pure  potassium  carbonate  are  added.  The  mass  is 
well  mixed,  washed  with  100  c.c.  of  water  into  a  beaker,  and 
is  allowed  to  settle.  In  a  few  minutes  the  liquid  becomes 
reddish-violet  if  alum  is  absent,  grayish-blue  to  deep  blue 
when  it  is  present. 

The  quantitative  estimation  of  the  alum  is  made  as  follows: 
The  ash  from  100  grams  or  more  of  the  bread  is  boiled  with 
hydrochloric  acid  and  the  solution  filtered.  The  filtrate  is 
boiled  and  added  to  a  concentrated  solution  of  sodium  hy- 
droxid,  the  mixture  being  again  boiled  and  filtered  while  hot. 
A  little  disodium  acid  phosphate  is  added  to  the  filtrate,  which 
is  then  slightly  acidulated  with  hydrochloric  acid  and  finally 
made  feebly  alkaline  by  addition  of  ammonium  hydroxid.  The 
precipitate  of  aluminum  phosphate  is  filtered,  washed,  ignited, 
and  weighed.  Flour  contains  a  small  proportion  of  aluminum, 
which,  in  the  ash,  is  probably  in  the  form  of  silicate.  The 
amount  of  silica  is  approximately  equal  to  that  of  alum  equiva- 
lent to  the  aluminum  normally  present.  It  is  the  practice, 
therefore,   to  determine  the  silica  and  subtract   it  from   the 


I04  FOOD   ANALYSIS 

amount  of  alum  calculated  from  the  aluminum  phosphate  found. 
The  remainder,  multiplied  by  3.8  or  3.7,  will  give  approximately 
the  potassium  alum  or  ammonium  alum  respectively. 

Copper  sulfate  may  be  detected  by  the  brown  produced 
when  a  thin  slice  of  bread  is  immersed  in  a  dilute  solution  of 
potassium  ferrocyanid. 

Foreign  flours  may  be  sought  for  by  the  microscope,  but 
the  starch  granules  are  usually  so  altered  by  heat  as  to  render 
identification  impossible. 

For  detection  of  maize  in  wheat  bread  and  pastry,  Ottolenghi 
proposes  the  following  test  based  on  the  reaction  of  proteids 
pecuHar  to  maize  as  elucidated  by  Donard  &  Labbe.^ 

100  grams  of  crumb  are  dried  at  40°,  powdered  finely,  treated 
with  500  c.c.  of  a  0.3  per  cent,  solution  of  potassium  hydroxid 
for  12  hours,  with  frequent  shaking.  The  liquid  is  strained 
through  muslin,  the  residue  again  treated  with  the  alkaline 
solution  for  3  hours,  after  which  the  mass  is  poured  on  the  muslin 
strainer  and  well  pressed.  The  filtrate  is  evaporated  below 
70°  to  dryness,  the  residue  broken  up  as  finely  as  possible, 
transferred  to  a  flask,  mixed  with  40  c.c.  absolute  iso-amyl 
alcohol,  an  inverted  condenser  is  attached  to  the  flask  and  the 
liquid  boiled  in  an  oil-bath  for  6  hours.  The  solvent  is  filtered 
hot.  If  no  maize  is  present,  the  yellowish-brown  filtrate  re- 
mains clear,  but  with  maize  it  becomes  turbid.  The  admixture 
of  the  filtrate  with  3  volumes  of  pure  benzene  increases  the  tur- 
bidity if  maize  is  present,  but  produces  no  effect  if  the  original 
substance  was  pure  wheat  flour. 

The  following  adulterants  are  said  to  be  employed  abroad, 
but  their  use  does  not  appear  to  have  been  attempted  in  this 
country : 

Soap  is  said  to  be  used  to  render  the  bread  light  and  soft. 
It  is  said  to  be  added  in  solution  containing  emulsified  oil. 

Terra  alba  and  gypsum  have  been  found;  they  are  readily 
detected  in  the  ash. 


LEAVENING  MATERIALS  105 

Stannous  chlorid  is  a  comrr|on  constituent  of  ginger  cake,  to 
which  it  is  added,  with  pota^ium  carbonate,  in  order  to  give 
the  product  the  color  ordinarily  produced  by  honey  or  mo- 
lasses. It  is  said  to  render  a  product  made  of  poor  flour  and 
molasses  of  the  same  color  as  that  produced  by  a  good  flour 
and  honey.     Tin  may  be  detected  as  described  on  page  59. 

LEAVENING  MATERIALS 

The  yeast  cakes  sold  for  leavening  purposes  are  usually 
mixtures  of  common  yeast  with  potato  starch.  The  study 
of  yeast  is  practically  limited  to  those  connected  with  the 
fermentation  industries.  Cream  of  tartar  and  baking  soda  are 
commonly  employed  as  leavening  agents. 

Baking  Soda,  Sodium  Acid  Carbonate,  is  not  subject  to 
serious  adulteration. 

Cream  oj  Tartar,  Acid  Potassium  Tartrate,  is  frequently 
adulterated  with  starch,  alum,  acid  calcium  phosphate,  calcium 
sulfate,  and  potassium  acid  sulfate.  Many  samples  will  be 
found  to  contain  no  tartrate,  but  merely  a  mixture  of  starch, 
calcium  phosphate,  and  alum. 

For  the  detection  of  tartaric  acid  see  under  "Fruit  Juices." 
If  starch  is  present  the  sample  should  be  treated  with  cold 
water  for  a  while,  filtered  and  the  residue  evaporated  on  the 
water  bath  and  tested. 

Allen  devised  the  following  method  for  the  examination  of 
commercial  cream  of  tartar : 

1. 881  grams  of  the  dried  material  are  dissolved  in  hot  water 
and  titrated  with  t,-  sodium  hydroxid  and  phenolphthalein. 
If  tartaric  acid  and  acid  sulfates  are  not  present,  each  c.c.  will 
represent  i  per  cent,  of  acid  potassium  tartrate. 

1. 881  grams  of  dried  material  are  ignited  for  10  minutes, 
the  residue  boiled  with  water,  filtered,  and  washed.  The 
filtrate  is  titrated  with   ^  hydrochloric  acid  and  methyl-orange. 


Io6  FOOD   ANALYSIS 

With  pure  tartrate  the  amount  of  acid  consumed  will  be  the 
same  as  that  of  the  alkali  in  the  first  experiment.  Each  cubic 
centimeter  of  deficiency  is  equivalent  to  0.36  per  cent,  calcium 
sulfate,  or  0.72  per  cent,  acid  potassium  sulfate.  If  the  amount 
of  acid  be  more  than  equivalent  to  that  of  the  alkali  used  in  the 
former  experiment,  it  suggests  the  presence  of  neutral  tartrate, 
each  cubic  centimeter  of  excess  representing  0.6  per  cent,  thereof. 
The  amount  of  sulfate  can  be  determined  by  precipitating  with 
barium  chlorid  in  the  usual  way. 

The  residue  is  ignited,  dissolved  in  20  c.c.  of  -^  acid,  filtered 
from  any  insoluble  residue,  and  the  filtrate  titrated  with  -^ 
alkali.  Each  c.c.  corresponds  to  0.5  per  cent,  of  calcium 
tartrate,  or  0.36  per  cent,  of  anhydrous  calcium  sulfate. 

The  cream  of  tartar  substitutes  commonly  sold  contain 
starch,  alum,  and  calcium  phosphate.  Starch  can  be  detected 
by  the  iodin  test  and  by  the  microscope.  Quantitative  examin- 
ation of  such  samples  will  be  conducted  as  described  under 
"Baking  Powders." 

Baking  Powders. — These  contain  acid  sodium  carbonate, 
some  acid  salt,  e.  g.,  acid  potassium  tartrate,  acid  calcium 
phosphate,  or  alum,  with  inert  material,  starch  or  flour,  to 
prevent  caking.  Many  powders  contain  both  alum  and  acid 
calcium  phosphate.  The  following  methods  for  examining 
baking  powders  were  published  by  Crampton : 

The  value  of  baking  powder  depends  on  the  gas  liberated 
when  it  is  mixed  with  water.  The  determination  may  be 
by  the  apparatus  of  Knorr  (figure  34).  The  flask  A  holds  the 
weighed  portion  of  sample.  The  condenser  D,  attached  by  a 
ground  joint,  serves  to  condense  the  steam  formed  when  the 
liquid  in  A  is  boiled.  B  contains  either  recently-boiled  water  or 
dilute  sulfuric  acid,  according  to  whether  the  available  carbon 
dioxid  or  total  carbonates  are  to  be  determined. 

It  has  a  soda-lime  tube  attached  by  a  ground-joint  to  pre- 


LEAVENING   MATERIALS  107 

vent  admission  of  carbon  dioxid  from  the  current  of  air  which 
is  drawn  through  the  apparatus  during  the  operation.  The 
junction  of  this  portion  with  the  fiask  should  be  by  ground 
or  fused  joint.  The  evolved  gas  is  dried  in  E  by  sulfuric 
acid  and  absorbed  in  F. 


Fig.  34. 

Available  carbon  dioxid,  which  gives  the  leavening  power, 
is  determined  as  follows:  The  flask  A  is  dried  thoroughly, 
a  weighing  tube  is  charged  with  about  2  grams  of  the  powder, 
accurately  weighed,  the  contents  emptied  into  the  flask,  and 
the  tube  weighed  again.     The  exact  amount  of  powder  taken 


Io8  FOOD   ANALYSIS 

is  thus  known.  Recently-boiled  water  is  put  into  B,  the 
apparatus  connected  tightly,  and  the  water  allowed  to  flow  in 
slowly  from  B,  the  aspirator  attached  to  G  being  put  in  opera- 
tion. When  the  effervescence  in  A  has  ceased,  the  liquid  in  it  is 
boiled  for  a  few  seconds,  the  lamp  removed,  and  aspiration 
through  G  continued  for  15  minutes.  The  absorption  ap- 
paratus F  is  weighed,  and  the  increase  represents  carbon  dioxid. 
Total  carbonates  are  determined  by  substituting  10  c.c.  dilute 
sulfuric  acid  for  the  water  in  B. 

Starch. — 5  grams  are  mixed  in  a  flask  with  200  c.c.  of  4  per 
cent,  hydrochloric  acid.  A  condensing  tube  about  i  meter 
long  is  attached  by  means  of  a  cork  (an  inverted  condenser  may 
be  used)  and  the  liquid  boiled  for  4  hours.  The  contents  are 
cooled,  rendered  slightly  alkaline  by  sodium  hydroxid,  and  the 
dextrose  determined  as  given,  and  multiplied  by  0.9. 

For  powders  not  containing  appreciable  amounts  of  alum, 
direct  washing  with  water,  and  drying  the  residue,  will  often 
give  determinations  of  sufficient  accuracy.  Since  the  residual 
liquid  in  properly-made  baking  powders  is  alkaline,  due  to 
slight  excess  of  baking  powder,  the  diastase  method  for  starch 
may  be  applicable.  The  liquid  should  be  filtered  and  the 
insoluble  residue  well  washed.  The  aluminum  hydroxid  may 
interfere  with  this  method.  If  flour  be  used  as  filler,  which 
may  be  ascertained  by  inspection,  the  starch  found  may  be 
roughly  calculated  to  flour  by  the  table  on  page  97. 

Aluminum  and  Phosphates. — McElroy  devised  the  following 
method :  5  grams  are  charred  in  a  platinum  basin,  mixed  with 
strong  nitric  acid,  and  filtered  into  a  500  c.c.  flask.  The 
residue  is  washed  slightly,  the  filter  and  residue  returned  to 
the  basin,  burned  to  whiteness,  mixed  with  sodium  carbon- 
ate, fused,  and  cooled.  Nitric  acid  is  added,  the  liquid  evapo- 
rated to  dryness,  again  acidified  with  nitric  acid,  and  the  whole 
mass  washed  into  the  500  c.c.  flask.  The  liquid  is  made  up  to 
the  mark  and  filtered  through  a  dry  filter,  100  c.c.  of  the  filtrate 


LEAVENING   MATERIALS  IO9 

are  nearly  neutralized  with  ammoniurn  hydroxid,  ammonium 
nitrate  and  ammonium  molybdatc  solution  added,  the  mass 
digested  at  a  low  heat  for  a  few  hours,  and  filtered.  The 
filtrate  contains  the  aluminum,  which  may  be  precipitated 
as  hydroxid  by  adding  ammonium  hydroxid.  The  precipitate 
is  dissolved  in  ammonium  hydroxid  and  the  phosphate  deter- 
mined in  the  usual  way. 

Calcium. — 5  grams  are  mixed  in  a  500  c.c.  flask  with  50 
c.c.  of  water  and  30  c.c.  of  strong  hydrochloric  acid,  the  mixture 
made  up  to  the  mark,  shaken  well,  and  allowed  to  settle.  50 
c.c.  are  collected  through  a  dry  filter,  nearly  neutralized  by 
ammonium  hydroxid,  acetic  acid  added  in  small  amount,  then 
ammonium  acetate,  and  the  liquid  boiled.  If  any  precipitate 
forms  it  should  be  removed.  The  clear  liquid  is  precipitated 
by  ammonium  oxalate. 

Suljates. — 0.5  gram  of  the  sample  are  digested  with  strong 
hydrochloric  acid  until  everything  has  dissolved,  the  liquid  is 
diluted  considerably,  brought  to  boiling,  and  precipitated  with 
barium  chlorid,  taking  care  not  to  use  a  large  excess.  The 
precipitate  is  weighed  in  the  usual  manner. 

Ammonium  Compounds. — These  may  be  determined  by 
adding  to  the  water  filtered  from  a  known  weight  of  the  powder 
sufficient  sodium  carbonate  to  make  it  distinctly  alkaline 
distilling  until  half  the  liquid  has  passed  over  and  titrating 
the  distillate  with  standard  acid. 

The  best  commercial  baking  powders  yield  about  12  per 
cent,  by  weight  of  gas.  10  grams  would,  therefore,  yield  1.2 
grams,  occupying  at  ordinary  temperature  about  600  c.c, 
which  will  be  much  increased  in  baking.  Many  powders 
yield  much  less  gas. 


no  FOOD   ANALYSIS 

SUGARS 

Detection. 

Most  of  the  tests  for  sugars  except  the  phenylhydrazin,  fer- 
mentation, and  optic  tests  depend  on  their  reducing  effect.  Su- 
crose possesses  less  reducing  action  than  other  common  sugars, 
does  not  give  any  precipitate  with  phenylhydrazin,  and  is  not 
directly  fermentable.  By  the  action  of  dilute  acids  or  inver- 
tase  (yeast-enzym)  it  is  converted  (hydrolyzed)  to  equal  parts 
of  dextrose  and  levulose,  a  change  commonly  termed  "in- 
version," the  mixture  being  known  as  "invert-sugar."  This 
responds  to  all  the  above  tests. 

Cobalt  Nitrate  Test. — Wiley  has  experimented  with  this 
method  and  has  obtained  satisfactory  results.  He  describes 
it  as  follows: 

5  c.c.  of  a  5  per  cent,  solution  of  cobaltous  nitrate  are  well 
mixed  with  15  c.c.  of  sugar  solution,  and  2  c.c.  of  a  50  per 
cent,  solution  of  sodium  hydroxid  added.  Sucrose  gives  an 
amethyst-violet  solution,  which  is  made  somewhat  more  blue 
by  boihng,  but  regains  its  color  on  cooling.  Dextrose  gives 
a  turquoise-blue,  which  in  the  course  of  two  hours  passes  into 
a  pale  green.  A  slight  fiocculent  precipitate  is  noticed  in  the. 
tube  containing  dextrose.  Maltose  and  lactose  act  very  much 
as  dextrose,  but  in  the  end  do  not  give  so  fine  a  green  color. 
If  the  solution  containing  dextrose,  lactose,  or  maltose  be 
boiled,  the  original  color  is  destroyed  and  a  yellow-green 
color  takes  its  place.  In  mixtures  of  dextrose  and  sucrose 
the  sucrose  coloration  predominates — one  part  of  sucrose  in 
nine  parts  of  dextrose  can  be  distinguished.  Impurities  such 
as  gum  arable  or  dextrin  should  be  removed  by  alcohol  or 
lead  subacetate  before  the  application  of  the  test.  Dextrin 
may  also  be  thrown  out  by  treatment  of  the  solution  with 
barium  hydroxid  and  ammoniacal  lead  acetate.  The  reaction 
may  be  applied  to  the  detection  of  cane-sugar  in  wines  after 


SUGARS  III 

they  are  thoroughly  decolorized  by  means  of  lead  acetate  and 
bone-black.  Sucrose  may  be  detected  in  fresh  or  condensed 
milk  after  the  disturbing  matters  have  been  thrown  out  by  lead 
acetate.     Sucrose  may  be  detected  in  honey. 

Phenylhydrazin  Test. — Phenylhydrazin  hydrochlorid  is  usu- 
ally employed.  The  commercial  article  is  often  contaminated 
with  anihn  hydrochlorid;  It  may  be  purified  by  solution  in  hot 
water,  precipitation  by  strong  hydrochloric  acid,  and  recrys- 
tallization  from  hot  water. 

For  the  test,  o.i  gram  of  the  sample,  about  0.2  gram  phenyl- 
hydrazin hydrochlorid,  and  0.3  gram  of  sodium  acetate  are 
dissolved  in  5  c.c.  of  water  and  heated  on  the  water-bath  for 
some  time.  Sucrose  forms  no  precipitate,  but  with  many 
sugars  crystalline  compounds  called  osazones  separate. 

Dextrose  and  levulose  yield  the  same  compound,  which 
may  be  termed  ''glucosazone."  It  crystallizes  in  needles 
melting  at  204-205°,  and  reduces  Fehling's  solution. 

Maltosazone  crystalhzes  in  plates  that  melt  with  decomposi- 
tion at  206°. 

Lactosazone  crystallizes  in  prisms  melting  at  200°. 

Sucrose  forms  no  osazone.  After  hydrolysis  it  yields  glu- 
cosazone. 

Lactose^  after  boiling  with  dilute  sulfuric  acid,  yields  a  mixture 
of  glucosazone  and  galactosazone.  The  latter  is  distinguished 
by  its  melting-point,  193°. 

Starch  and  dextrin^  after  hydrolysis,  yield  maltosazone  and 
glucosazone. 

Maltose  and  lactose  produce  with  ammonium  hydroxid  a 
characteristic  red,  a  reaction  that  distinguishes  them  from  other 
common  carbohydrates.  Wohlk,^^  to  whom  this  test  is  due, 
describes  the  following  manipulation: 

About  0.6  gram  of  the  sample  are  dissolved  in  a  test  tube  in 
10  c.c.  of  10  per  cent,  ammonium  hydroxid  and  the  tube  im- 
mersed in  water  that  has  just  ceased  boiling.     This  causes  the 


112  FOOD   ANALYSIS 

ammonium  hydroxid  to  pass  off  without  the  liquid  reaching  the 
boihng-point  or  being  ejected.     In  about  20  minutes  the  color 
appears. 
Determination. 

The  preparation  of  sucrose  for  use  as  a  standard  in  polar- 
imetry  and  reduction-tests  was  the  subject  of  formal  action 
at  the  third  session  of  the  International  Commission  for  Uni- 
jorm  Methods  oj  Sugar  Analysis,  Paris,  July  24,  1900. 

Purest  commercial  sugar  is  selected  and  dissolved  by  satu- 
ration in  hot  water,  and  ethyl  alcohol  added  sufficient  to  pre- 
cipitate the  sugar.  The  precipitate  is  whirled  in  a  centrifuge 
and  washed  with  alcohol.  The  material  obtained  is  put  through 
the  whole  process  a  second  time,  and  the  washed  material  is 
dried  on  pure  bibulous  paper  and  kept  in  stoppered  glass  ves- 
sels. It  still  contains  moisture,  which  must  be  determined 
and  allowed  for  in  making  standard  solutions. 

The  temperature  of  the  water  is  not  given.  Blotting-paper 
is  mentioned  in  the  original  test,  but  filter-paper  is  better,  as 
commercial  blotting-paper  is  of  uncertain  composition. 

For  the  standardization  of  solutions  for  the  determination  of 
sucrose  and  invert-sugar,  2.5  grams  of  pure  sucrose  should 
be  dissolved  in  a  mixture  of  75  c.c.  of  water  and  5  c.c.  of  hy- 
drochloric acid  (sp.  gr.  1.188  at  15°),  hydrolyzed  according 
to  the  method  on  page  119,  the  acid  neutralized  with  sodium 
carbonate,  and  the  solution  diluted  to  one  liter.  2.5  grams  of 
sucrose  yield  2.6316  grams  of  invert-sugar.  The  number  of 
cubic  centimeters  of  sugar  solution  used,  multiplied  by  0.00263, 
will  give  the  weight  of  invert-sugar  required  to  reduce  com- 
pletely 10  c.c.  of  the  test  solution  under  the  conditions  of  the 
experiment. 

CHEMICAL   METHODS. 

These  methods,  when  applied  to  the  determination  of  sucrose, 
must  be  preceded  by  hydrolysis,  for  which  see  page  119. 
The  following  are  standard  reagents : 


SUGARS  113 

soxhlet's  modified  copper  solution  (a.  o.  a.  c). 

Copper  suljate  solution.  34.639  grams  of  pure  crystallized 
copper  sulfate  are  dissolved  in  sufficient  water  to  make  500  ex. 

Alkaline  tartrate  solution.  173  grams  of  pure  potassium 
sodium  tartrate  and  50  grams  of  sodium  hydroxid  are  dis- 
solved in  sufficient  water  to  make  100  c.c.  A  convenient 
method  is  to  use  100  c.c.  of  a  solution  containing  500  grams 
of  sodium  hydroxid  in  one  liter. 

Potassium  acid  tartrate,  now  obtainable  of  very  good  quality, 
may  be  used  instead  of  potassium  sodium  tartrate,  in  which 
case  the  proportion  required  will  be  133  grams  of  potassium 
acid  tartrate  and  80  grams  of  sodium  hydroxid  made  up  to  500 
c.c.  The  copper  and  alkaline  tartrate  solutions  must  be  kept 
separate  in  well-stoppered  bottles  and  mixed  only  when  needed. 
approximate  volumetric  method  for  rapid  work. 

5  c.c.  of  each  of  the  solutions  are  placed  in  a  large  test-tube, 
10  c.c.  of  distilled  water  added,  the  liquid  heated  to  boiling, 
and  small  portions  of  the  solution  to  be  tested  gradually  added 
until  the  copper  has  been  completely  precipitated,  boiling  to 
complete  the  reaction  after  each  addition.  When  the  end 
reaction  is  nearly  reached  and  the  amount  of  sugar  solution 
can  no  longer  be  judged  by  the  color  of  the  solution,  a  small 
portion  of  the  liquid  is  removed  by  means  of  a  filtering-tube, 
placed  in  a  porcelain  crucible  or  on  a  testing  plate,  acidified 
with  dilute  acetie  acid,  and  tested  for  copper  by  solution  of 
potassium  ferrocyanid.  The  sugar  solution  should  be  of  such 
strength  as  will  require  from  15  to  20  c.c.  to  complete  the 
reduction,  and  the  number  of  additions  of  solution  should  be 
as  few  as  possible.  It  is  best  to  verify  the  first  experiment 
by  a  second,  based  on  the  approximation  which  the  first  gives. 
Boiling  for  2  minutes  should  be  required  for  complete  precipi- 
tation when  the  full  amount  of  sugar  solution  has  been  added  in 
one  portion.  The  factor  for  calculation  varies  with  the  minute 
details  of  manipulation;    every  operator  must  determine  the 


114 


FOOD   ANALYSIS 


individual  factor  by  using  a  known  amount  of  the  form  of  sugar 
that  is  to  be  determined  and  maintaining  conditions  as  uniform 
as  possible. 

Figure  35  shows  filter-tubes  suitable  for  obtaining  a  small 
quantity  of  the  liquid.  Wiley's  tube  (A)  is  a  thick- walled  glass 
tube  about  4  cm.  long  on  one  of  which  a  flange  has  been  made, 
over  which  a  piece  of  fine  linen  is  tied.  Knorr's  tube  (B)  is 
much  narrower,  and  has  a  perforated  platinum 
disk  sealed  into  the  lower  end.  The  tube  is 
dipped  into  water  containing  suspended  asbes- 
tos, and  by  aspiration  a  thin  felt  is  formed  over 
the  lower  surface  of  the  platinum  disk.  The 
tube,  thus  prepared,  is  dipped  into  the  boiling 
copper  solution  and  by  aspiration  a  drop  is 
drawn  into  the  tube.  The  Wiley  filter  requires 
that  the  liquid  be  poured  from  the  tube  when 
it  is  to  be  tested,  but  with  the  Knorr  tube  the 
asbestos  is  wiped  off,  the  liquid  expelled  through 
the  platinum,  and  the  drop  is  tested  for  copper 
as  noted. 

Another  method  is  to  remove  a  drop  of  the 
boiling  solution  by  means  of  a  rod  and  place 
it  on  a  piece  of  pure  filter-paper.  The  pre- 
cipitate remains  in  the  center  of  the  moistened 
spot.  A  drop  of  potassium  ferrocyanid  solu- 
FiG.  35.  tion,  acidulated  with  acetic  acid,  is  then  placed 

near  it ;  as  the  spot  spreads,  a  brown  stain  will 
appear  where  the  liquids  meet,  if  copper  still  be  in  solution. 
soxhlet's  exact  method. 

An  approximate  determination  of  the  reducing  sugars  in 
the  sample  is  made  by  one  of  the  titration  methods  and  a 
solution  is  prepared  which  contains  nearly,  but  not  more  than, 
I  per  cent,  of  these  sugars.  50  c.c.  of  copper  sulfate  solution 
and  50  c.c.  of  alkaline  tartrate  solution  are  mixed,  added  to  a 


SUGARS 


II 


volume  of  the  solution  of  the  sample  estimated  to  be  suffi- 
cient for  the  complete  precipitation  of  the  copper,  boiled  for 
2  minutes,  some  of  the  solution  filtered  rapidly,  and  the  filtrate 
tested  for  copper.  The  process  is  repeated  until  two  proportions 
of  the  solution  of  the  sample  are  determined  which  differ  by 
O.I  c.c,  one  giving  complete  reduction  and  the  other  leaving 
a  small  amount  of  copper  in  solution.  The  means  of  these 
volumes  is  the  amount  of  solution  required  for  the  volume  of 
Fehling  solution  taken. 

Under  these  conditions,  which  must  be  rigidly  observed,  the 
volume  of  solution  used  will  contain  0.475  gram 
of  dextrose  or  0.494  gram  of  invert-sugar.  As 
the  weight  of  the  sample  which  is  in  this  amount 
of  solution  is  known,  the  percentage  of  either 
sugar  may  be  calculated  by  simple  proportion. 
allihn's  method  for  dextrose. 

Copper  suljate  solution.     See  page  113, 

Alkaline  tartrate  solution.  1 73  grams  of  pure 
potassium  sodium  tartrate  and  125  grams  of 
potassium  hydroxid  are  dissolved  in  water  and 
made  up  to  500  c.c. 

The  substance  to  be  tested  is  dissolved  in 
water  in  such  proportion  that  the  solution  shall 
not  contain  more  than  i  per  cent,  of  dextrose. 
30  c.c.  of  each  of  the  reagent  solutions  and  60  c.c.  of  water  are 
mixed  and  heated  to  boiling,  25  c.c.  of  the  solution  to  be  exam- 
ined are  added,  the  boiling  continued  for  2  minutes,  and  the  liquid 
immediately  filtered  without  dilution,  as  directed  in  connection 
with  the  reduction  or  electrolytic  methods  of  determination  of 
copper. 

The  precipitated  cuprous  oxid  is  usually  converted  into  free 
copper  and  weighed  as  such.  Two  methods  may  be  employed 
for  reduction :  by  hydrogen  or  by  electrolysis. 

Reduction  by  Hydrogen. — The  cuprous  oxid  is  collected  on  an 


F'IG.  36. 


Il6  FOOD   ANALYSIS 

asbestos  filter.  This  is  arranged  most  conveniently  in  a  special 
filtering  tube,  which  is  shown  in  figure  36.  The  wider  part  is 
about  8  cm.  long  and  1.5  cm.  in  diameter,  the  narrower  portion 
about  5  cm.  long  and  0.5  cm.  in  caliber.  A  perforated  platinum 
disk  is  sealed  in  just  above  the  point  of  narrowing.  The  asbes- 
tos is  placed  on  this  disk,  washed  free  from  loose  fibers,  dried 
well  and  the  tube  weighed.  The  filtering  tube  is  attached  to  an 
exhaustion  apparatus  by  passing  narrower  portion  through  the 
cork,  and  a  small  funnel  is  fitted  tightly  in  the  top  of  the  tube. 
The  object  of  this  funnel  is  to  prevent  the  precipitate  collect- 
ing on  the  upper  part  of  the  tube.  The  lower  end  of  the 
funnel  should  project  several  centimeters  below  the  bottom  of 
the  cork  through  which  it  passes. 

The  filtering  apparatus  must  be  arranged  prior  to  the  pre- 
cipitation, so  that  the  cuprous  oxid  may  be  filtered  without 
delay.  The  precipitate  is  transferred  as  rapidly  as  possible 
to  the  filter,  well  washed  with  hot  water,  alcohol,  and  ether 
successively,  dried,  and  the  cuprous  oxid  reduced  by  gentle 
heating  in  a  current  of  dry  hydrogen.  When  the  reduction 
is  complete,  the  heat  is  withdrawn,  but  the  flow  of  hydrogen 
is  continued  until  the  tube  is  cold.  It  is  then  detached  and 
weighed.  The  amount  of  sugar  is  determined  by  reference  to 
the  table  on  page  117.  Quantities  of  copper  intermediate  be- 
tween those  given  in  the  table  may  be  converted  into  the  equiva- 
lent in  sugar  by  allowing  for  each  o.ooi  of  copper,  0.0005  of 
dextrose  for  figures  in  the  first  column,  0.00055  for  figures  in  the 
second  column,  and  0.0006  in  the  third  column. 

Reduction  of  Copper  by  Electrolysis. — The  filtration  is  per- 
formed in  a  Gooch  crucible  with  an  asbestos-felt  film  and  the 
beaker  in  which  the  precipitation  was  made  is  well  washed 
with  hot  water,  the  washings  being  passed  through  the  filter, 
but  it  is  not  necessary  to  transfer  all  the  precipitate.  When 
the  asbestos  film  is  completely  washed,  it  is  transferred  with 
the  adhering  oxid  to  the  beaker;    any  oxid  remaining  in  the 


(university  j 


SUGARS 


117 


crucible  is  washed  into  the  beaker  by  use  of  2  c.c.  nitric  acid 
(sp.  gr.  1.42),  added  with  a  pipet.  The  crucible  is  rinsed 
with  a  spray  of  water,  the  rinsings  being  collected  in  the  beaker. 
The  liquid  is  heated  until  all  the  copper  is  in  solution,  filtered, 
the  filter  washed  until  the  filtrate  amounts  to  at  least  100  c.c, 
and  electrolyzed. 


EQUIVALENTS  FOR 

ALLIHN'S  METHOD 

Copper. 

Dextrose. 

Copper. 

Dextrose. 

Copper. 

Dextrose. 

O.OIO 

0.0061 

0.170 

0.0869 

0.330 

0.1 731 

0.020 

O.OIIO 

0.180 

0.0921 

0.340 

0.1787 

0,030 

0.0160 

0.190 

0.0973 

0.350 

0.1843 

0.040 

0.0209 

0.200 

0. 1026 

0.360 

0.1900 

0.050    » 

0.0259 

0.210 

0. 1079 

0.370 

0.1957 

0.060 

0.0308 

0.220 

0.II32 

0.380 

0.2014 

0.070 

0.0358 

0.230 

0.1 185 

0.390 

0.2071 

0.080 

0.0408 

0.240 

0.1239 

0.400 

0.2129 

0.090 

0.0459 

0.250 

0.1292 

0.410 

0.2187 

0. 100 

0.0509 

0.260 

0.1346 

0.420 

0.2245 

0.1 10 

0.0560 

0.270 

0. 1400       j 

0.430 

0.2304 

0.120 

0.061 1 

0.280 

0.1455        j 

0.440 

0.2363 

0.130 

0.0662 

0.290 

0.1510       , 

0.450 

0.2422 

0.140 

0.0713 

0.300 

0.1565 

0.460 

0.2481 

0.150 

0.0765 

0.310 

0.1620 

0.463 

0.2499 

0.160 

0.0817 

0.320 

0.1675 

0.465 

0.2511 

Electrolytic  apparatus  has  been  constructed  in  a  great  variety 
of  forms.  When  the  operation  is  carried  out  frequently,  it  is 
best  to  have  an  electrolytic  table.  A  platinum  basin  holding 
not  less  than  100  c.c.  is  used.  A  cylindrical  form  with  flat 
bottom  is  convenient.  It  should  rest  on  a  bright  copper  plate, 
which  is  connected  with  the  negative  pole  of  the  electrical 
supply.  The  positive  pole  should  be  also  platinum,  either  a 
spiral  wire,  cylinder,  or  flat  foil.  Many  operators  use  a  funnel- 
shaped  perforated  terminal  for  the  negative  pole ;  in  which  case 
a  glass  beaker  or  casserole  will  be  a  suitable  container,  the  posi- 
tive terminal  being  placed  within  the  negative. 


Il8  FOOD   ANALYSIS 

Four  cells  of  a  gravity  battery  will  suffice  for  a  single  de- 
composition, and  will  operate  two,  but  more  slowly.  It  is 
usual  to  arrange  the  apparatus  so  that  the  operation  may  be 
continued  during  the  night.  When  the  electricity  is  taken 
from  the  general  supply  of  the  laboratory,  it  is  usually  neces- 
sary to  interpose  resistance  and  to  have  some  means  of  meas- 
uring the  current-flow.  This  is  sometimes  done  with  a  gas 
evolution  cell  and  incandescent  lamp,  but  an  ammeter  and 
adjustable  rheostat  is  better. 

OPTIC   METHODS. 

The  general  principles  of  polarimetry  have  been  explained 
elsewhere.  For  the  decolorization  and  clarification  of  solu- 
tions, the  following  standard  reagents  are  employed : 

Lead  suhaceiate.  Solution  of  lead  acetate  is  boiled  with 
excess  of  lead  monoxid  for  30  minutes,  filtered,  and  brought 
to  a  specific  gravity  of  1.250.  Sohd  lead  subacetate  may  be. 
used  in  preparing  the  solution. 

The  clarification  of  sugar  solutions  may  often  be  more  con- 
veniently effected  by  the  addition  of  solid  lead  subacetate,  ac- 
cording to  the  suggestion  of  Horne.^^  The  weighed  material  is 
dissolved  in  water  and  made  up  to  100  c.c.  Finely-powdered 
lead  subacetate  is  added  in  small  quantities,  with  shaking  until 
the  precipitation  is  complete,  allowing  each  portion  to  dissolve 
before  adding  more.  When  the  last  portion  has  dissolved, 
the  solution  is  shaken,  filtered  and  the  reading  taken.  No 
allowance  for  precipitate  is  required. 

Excess  of  lead  may  be  removed  from  these  solutions  by 
Sawyer's  method.^^  A  solution  of  double  normal  potassium 
oxalate  (184.4  grams  in  1000  c.c.)  is  used.  10  c.c.  of  this  are 
added  to  80  c.c.  of  the  clarified  solution,  allowed  to  stand  at 
room  temperature  for  15  minutes,  and  filtered.  The  oxalate 
is  in  large  excess;  this  does  not  interfere  with  the  polarization 
but  renders  the  precipitate  granular  and  easily  filtered. 

Alumina-cream.     A    cold    saturated    solution    of    alum    is 


SUGARS  119 

divided  into  two  unequal  portions;  a  slight  excess  of  ammo- 
nium hydroxid  is  added  to  the  larger  portion  and  the  remainder 
is  added  until  a  faintly  acid  reaction  is  obtained. 

For  sugars  and  molasses  the  normal  weight  for  the  instrument 
is  weighed  out,  washed  into  a  100  c.c.  flask,  and  water  added  to 
make  about  80  c.c.  When  the  material  has  dissolved  as  far  as 
possible,  lead  subacetate  is  added  until  all  precipitable  matter 
has  separated.  (With  molasses  sufficient  acetic  acid  should  be 
added  to  convert  the  lead  subacetate  into  acetate.)  The  flask 
is  filled  to  the  mark, — using,  if  necessary,  a  little  ether  spray  to 
break  bubbles, — filtered  with  a  dry  filter,  the  first  15  c.c.  re- 
jected, and  the  reading  taken  on  the  remainder  of  the  filtrate. 
If  the  liquid  is  very  dark,  some  dry  finely-powdered  pure  bone- 
black  should  be  used  instead  of  paper  and  the  first  40  c.c.  of 
filtrate  rejected.  All  observations  should  be  made  as  nearly  as 
possible  at  the  temperature  for  which  the  instrument  is  adjusted. 
A  change  of  5°  in  the  interval  between  filling  the  flask  and 
making  the  reading  will  cause,  by  change  of  volume,  an  error  of 
about  0.1  per  cent,  in  samples  containing  90  per  cent,  of  sucrose 
and  an  error  of  about  0.5  per  cent,  in  samples  containing  50  per 
cent,  of  sucrose. 

With  juices  or  other  dilute  materials,  weighing  may  be 
omitted,  and  100  c.c.  of  the  sample  measured  off,  powdered  lead 
subacetate  added  (page  118),  filtered  and  a  reading  taken. 

A.  O.  A.  C.  INVERSION   METHOD    (hYDROLYSIS). 

A  clear  solution  is  made  according  to  one  of  the  methods 
given  above.  50  c.c.  of  the  filtrate  are  placed  in  a  flask  marked 
at  50  and  55  c.c,  5  c.c.  of  pure  fuming  hydrochloric  acid  added, 
and  the  liquids  well  mixed.  The  flask  is  heated  in  water  until 
the  thermometer,  with  the  bulb  as  near  the  center  of  the  solution 
as  possible,  marks  68°.  About  15  minutes  should  be  required 
for  this  heating.  The  flask  is  then  removed,  cooled  quickly 
to  room  temperature,  and  polarized,  noting  the  temperature. 
If  the  sample  originally  contained  invert-sugar,   the  secoud 


I20  FOOD   ANALYSIS 

polarization  should  be  made  at  approximately  the  same  tem- 
perature as  the  first.  The  calculation  of  the  amount  of  sucrose 
is  made  by  the  following  formula : 

S  =  - 


143 -i 

2 


a  being  the  first  and  h  the  second  reading,  which  are  added 
when  of  opposite  signs  and  subtracted  when  of  like  signs ; 
that  is,  the  algebraic  difference  is  taken,  in  either  case. 

With  dark-colored  materials  it  will  often  be*  advantageous 
to  add  an  excess  of  alumina  cream.  Alumina  cream  alone 
will  often  suffice  for  clarification. 

When  lead  subacetate  is  used  with  liquids  containing  levu- 
lose,  it  is  usual  to  render  the  filtrate  acid  in  order  to  break 
up  a  compound  which  the  levulose  forms  with  lead,  but  it  is 
likely  that  potassium  oxalate  method  (page  1 1 8)  would  be  satis- 
factory. 

Hydrochloric  acid  affects  slightly  the  rotatory  power  of  these 
solutions.  In  observations  at  high  temperatures,  the  expansion 
of  the  liquid  also  introduces  an  error.  These  interferences 
are  usually  disregarded  in  food  analysis. 

GERMAN  OFFICIAL  METHOD. 

26.048  grams  of  the  sample  are  dissolved  in  a  sugar  flask  and 
the  solution  made  up  to  100  c.c;  50  c.c.  of  this  solution  are 
transferred  by  means  of  a  pipet  to  a  flask  graduated  at  50  and 
55  c.c,  enough  lead  subacetate  solution  added  for  clarification, 
the  volume  made  up  to  the  55  c.c.  mark,  and  the  liquid  thor- 
oughly shaken  and  filtered.  The  filtrate  is  then  polarized,  the 
reading  being  corrected  for  the  extra  5  c.c.  The  liquid  ad- 
hering to  the  pipet  is  washed  into  the  100  c.c.  flask  containing 
the  remaining  50  c.c.  (13.024  grams),  5  c.c.  of  concentrated 
hydrochloric  acid  (38  per  cent.,  specific  gravity  1.188  at  15°) 
added,  and  the  flask  placed  in  a  water-bath  the  temperature  of 


SUGARS  121 

which  is  70°.  The  contents  of  the  flask  should  reach  a  tem- 
perature of  67^-70°  in  two  or  three  minutes,  when  the  tem- 
perature should  be  maintained  within  this  limit  for  exactly  five 
minutes,  keeping  the  temperature  as  nearly  69°  as  possible. 
(See  international  agreement,  page  21,  as  to  standard  weight 
of  sugar.) 

SUCROSE 

Under  the  term  sucrose  all  forms  of  table  sugar  are  included. 
The  principal  sources  are:  the  sugar-cane,  Saccharum  offici- 
narum  L. ;  beet.  Beta  vulgaris  L. ;  sorghum,  Sorghum  sacchar- 
atum  Persoon;  sugar  maple,  Acer  saccharinum  L.  In  the 
crude  state  there  is  a  noticeable  difference,  but  so  far  as  is 
known,  the  sucrose  is  identical  in  all  cases. 

Adulterations  are  few.  The  addition  of  glucose,  especially 
to  the  lower  grades,  formerly  extensively  practised,  now  rarely 
occurs.  The  difference  in  the  grades  depends  largely  upon  the 
extent  to  which  the  molasses  and  mineral  matter  have  been 
removed.  Maple  sugar  is  sold  in  the  crude  condition  and  is 
often  adulterated. 

The  usual  examination  of  commercial  sugar  is  determina- 
tion of  the  amount  of  water,  ash,  sucrose,  and  reducing  sugar. 
Water  and  ash  are  determined  as  on  pages  27  and  39.  In 
the  best  grades  of  sugar  these  wjll  often  not  amount  to  more 
than  0.1  per  cent.  In  the  lower  grades  ash  may  be  3  per  cent., 
and  water  between  10  and  15  per  cent.  The  higher  proportions 
of  ash  are  found  in  beet-sugar.  The  estimation  of  sucrose  is 
most  conveniently  made  by  the  polarimeter.  The  direct  read- 
ing is  usually  sufficient,  but  the  result  may  be  checked  by 
hydrolysis,  and  reading  at  ordinary  temperature  and  at  86°. 
The  best  grades  will  give  a  direct  reading  closely  approximat- 
ing 100  per  cent.  In  some  cases  the  direct  reading  will  slightly 
exceed  icx),  due  to  a  small  proportion  of  rafhnose.  The  lower 
grades  of  sugar  contain  some  invert-sugar,  and  the  proportion 


122  FOOD   ANALYSIS 

of  sucrose  may  be  even  below  80  per  cent.  Maple  sugar  usually 
contains  about  85  per  cent,  of  sucrose. 

Coloring-matters. — Granulated  and  loaf  sugars  often  con- 
tain ultramarine  blue,  added  to  improve  color.  It  may  be 
separated  by  dissolving  a  considerable  quantity  of  the  sample 
in  water,  allowing  the  coloring-matter  to  subside,  and  washing 
it  with  water  several  times  by  decantation.  Ultramarine  blue 
is  decomposed  by  hydrochloric  acid,  the  color  discharged, 
and  hydrogen  sulfid  Uberated. 

Tin  chlorid  is  sometimes  employed  in  order  to  give  sugar 
a  bright,  lasting,  yellow  tint.  The  color  appears  to  be  the 
result  of  action  on  the  sucrose.  As  a  rule,  the  finished  product 
contains  but  traces  of  tin,  the  greater  portion  being  removed 
with  the  molasses.  The  so-called  Demerara  sugar  is  prepared 
in  this  way.  Demerara  sugar  is  frequently  imitated  by  the 
addition  of  artificial  coloring,  usually  to  beet-sugar.  To  sepa- 
rate such  added  coloring-matter  Cassel  recommends  the 
following  method : 

About  100  grams  of  the  sample  are  shaken  with  alcohol  of 
90  per  cent.  This  will  often  remove  the  color  in  a  single 
washing.  In  some  cases  it  is  advisable  to  use  alcohol  of  75 
or  80  per  cent.  The  solution  is  filtered  from  the  sugar,  evap- 
orated to  dryness,  the  color  again  taken  up  with  alcohol, 
and  a  skein  of  silk  or  wool  (preferably  slightly  mordanted 
with  aluminum  acetate)  treated  with  the  solution,  warmed  for 
some  time,  and  subsequently  well  washed  with  water.  The 
skein  will  be  dyed  of  a  more  or  less  yellow  color  in  the  presence 
of  artificial  dye.  A  sample  containing  only  such  coloring- 
matter  as  is  natural  to  sugar,  even  by  repeated  washing  with 
alcohol  of  90  per  cent.,  does  not  leave  absolutely  colorless 
crystals,  and  does  not  give  a  solution  capable  of  permanently 
dyeing  silk  or  wool.  It  is  probable  that  the  wool  test  described 
on  page  64  might  be  successfully  apphed  to  a  solution  in  water. 
See  also  Crampton  &  Simon's  test  for  caramel ^  page  125. 


SUGARS  123 

The  occasional  occurrence  of  artificial  sweetening  substances 
(e.  g.  saccharin,  glucin)  as  substitutes  for  sugar  in  confections, 
fruit  juices,  jams,  and  similar  articles  must  not  be  overlooked. 
The  possibility  of  commercial  glucose  and  invert-sugar  con- 
taining arsenic  and  lead  derived  from  the  sulfuric  acid  must  also 
be  borne  in  mind. 

MOLASSES   AND   SIRUP 

Molasses  is  the  uncrystallizable  sirup  produced  in  the 
manufacture  of  sugar.  It  properly  differs  from  treacle  in  that 
it  comes  from  sugar  in  the  process  of  making,  while  treacle  is 
obtained  in  the  process  of  refining,  but  the  two  terms  are  often 
employed  interchangeably.  Treacle,  often  called  refiner's 
molasses,  may  contain  35  per  cent,  or  more  of  sucrose,  which 
is  prevented  from  crystallizing  by  the  associated  substances. 
Ordinary  table-molasses  is  made  from  cane,  sorghum,  or 
maple.  Molasses  from  raw  cane-sugar  contains  considerable 
invert-sugar,  from  which  beet-root  molasses  is  comparatively 
free.  The  latter,  however,  contains  raffinose  and  a  great 
variety  of  other  bodies;  the  proportion  of  salts  being  some- 
times 15  per  cent.  These  impurities  render  it  unfit  for  table 
use.  Beet-sugar  partially  or  wholly  refined  is  free  from  these 
ingredients  and  may  be  used  in  the  preparation  of  table  sirups. 

Maple  sirup  is  molasses  from  the  maple.  Some  so-called 
maple  sirup  or  "mapleine"  is  made  by  addition  of  extract  of 
hickory-bark  to  sucrose  or  glucose  sirup. 

Molasses  and  maple  sirup  are  often  adulterated  by  the  addi- 
tion of  glucose  sirup.  The  product  is  usually  sold  as  molasses, 
but  is  sometimes  designated  "mixed  goods"  or  "table  sirup." 
Glucose  sirup  produces  a  pale  liquid,  of  good  body,  and  many 
samples  consist  almost  entirely  of  this  material,  flavored  by 
the  addition  of  a  small  proportion  of  the  lowest  grades  of  refuse 
molasses. 

The  addition  of  glucose  to  molasses  is  readily  detected  by 


124  FOOD   ANALYSIS 

means  of  the  polariscope.  The  normal  or  half  normal  quantity 
for  the  instrument  is  prepared  as  described  on  page  119  and  the 
reading  taken.  A  portion  of  this  solution  is  hydrolyzed,  as 
described  on  page  118,  and  two  readings  taken,  one  at  or  near 
the  same  temperature  as  the  direct  reading,  and  a  second  at  86° 
(see  page  17).  Pure  molasses  generally  gives  on  direct 
reading  at  a  temperature  of  20°  a  deviation  corresponding  to 
40  or  50  on  the  cane-sugar  scale.  After  hydrolysis,  the  reading 
at  the  same  temperature  will  be  — 10  or — 20,  and  at  a  tempera- 
ture of  86°  will  be  zero  or  near  it.  Sirups  made  by  the  solution 
of  sucrose  in  water  will  usually  give  a  rather  higher  direct 
reading,  but  after  hydrolysis  the  results  will  be  the  same  as  with 
molasses.  In  the  presence  of  any  considerable  quantity  of 
glucose  the  direct  reading  is  nearly  always  above  60  and  may 
rise  to  120  or  more.  After  hydrolysis,  the  sample  remains 
strongly  dextrorotatory  even  at  86°.  For  determination  of 
glucose  see  page  126. 

Dark  molasses  is  often  bleached.  Bone-black  is  sometimes 
used,  but  ozone,  hydrogen  dioxid,  sulfurous  acid,  sulfites,  and 
sulfuric  acid  have  been  employed.  One  method  consists 
in  the  addition  of  zinc  dust  and  sodium  sulfite,  the  zinc  being 
subsequently  removed  by  the  addition  of  oxalic  acid.  The 
bleached  molasses  is  liable,  therefore,  to  contain  either  zinc 
or  oxalic  acid. 

As  noted  above,  some  samples  of  sugar  are  prepared  by 
the  use  of  stannous  chlorid;  the  latter  may  pass  into  the  mo- 
lasses in  such  proportion  as  to  be  dangerous.  Copper  is  occa- 
sionally present,  derived  from  the  apparatus  of  the  refinery. 
For  the  detection  of  metallic  impurities  in  molasses,  not  less 
than  50  grams  should  be  ashed  and  examined  as  described 
on  page  40. 

The  U.  S.  standard  for  molasses  is  not  more  than  25  per  cent, 
of  water  nor  more  than  5  per  cent,  of  ash. 

Caramel  is  a  dark  brown  mass,  soluble  in  water  and  weak 


SUGARS  125 

alcoholic  liquids,  obtained  by  heating  sucrose  to  about  200°. 
It  is  largely  used  as  a  coloring-matter  in  foods  and  beverages. 
It  is  now  occasionally  adulterated  or  imitated  by  artificial 
coal-tar  colors.  The  wool  test  will  serve  in  many  cases  to 
detect  these.  Caramel  as  a  coloring  agent  is  most  easily 
recognized  by  a  method  due  to  Crampton  &  Simons:  The 
liquid  is  well  shaken  with  a  small  quantity  of  fuller's  earth 
and  filtered.  Coloring  matters  from  charred  or  uncharred 
wood  are  not  removed,  but  if  caramel  be  present  the  filtrate  will 
be  noticeably  paler  than  the  original  liquid.  See  also  under 
"Alcoholic  Beverages." 


GLUCOSE 

Commercial  glucose  consists  principally  of  dextrose  with 
considerable  maltose  and  gallisin  and  some  dextrin.  In  trade 
the  term  "glucose"  is  restricted  to  the  sirup;  the  solid  is 
called  "grape-sugar."  Inferior  quahties  of  glucose  may  con- 
tain sulfurous  or  sulfuric  acid,  calcium  sulfate,  arsenic,  and 
lead.     Glucose  is  often  termed  "corn  sirup." 

The  following  are  analyses  of  commercial  glucoses;  Nos.  i 
and  2  are  by  Moritz  &  Morris,  3  and  4  by  Stern.  In  Stern's 
analyses  some  figure  has  been  determined  by  difference,  prob- 
ably that  given  as  "  unfermentable  bodies,"  in  which  the  gallisin 
and  nitrogenous  matters  are  included. 


Dextrose, 

Maltose, 

Dextrin, 

Gallisin, 

Nitrogenous  matters, . . 
Unfermentable  bodies, 

Ash, 

Water, 


No.  I 

50.58 

No.  2. 

47-71 

No.  3. 
70.0 

No.  4. 
67.4 

14.19 
1.76 

12.29 
2.98 

5-1 

II.O 

15-59 
1. 18 

15.90 
0.81 

14.08 

4-3 

1.44 

1-39 

0.2 

1.6 

16.49 

20.77 

9.9 

15-7 

101.23         101.85         lOO.O 


126  FOOD   ANALYSIS 

Leach  ^^  found  that  the  glucose  commonly  used  in  adulterating 
molasses,  maple  sirup  and  honey  gives  a  direct  reading  of  87.5 
with  a  half-normal  weight  and  200  mm.  tube,  equivalent  to  a 
full  reading  of  175.  He  has,  therefore,  proposed  to  calculate 
the  glucose  on  this  basis,  by  the  following  formula : 

„        100  (a  — 5) 

This  may  be  simpUfied  to : 

0  =  0.561  (a  — S) 

in  which  G  is  glucose,  S,  sucrose  and  a  the  polarimetric  read- 
ing before  hydrolysis.  The  amount  of  sucrose  must  be  calcu- 
lated by  the  formula  on  page  120  from  the  reading  before  and 
after  inversion.  Some  samples  used  for  jellies  and  jams  may 
show  a  reading  as  low  as  150.  If  glucose  of  this  quality  is 
suspected,  the  constant  in  the  above  formula  should  be  0.666. 
The  method  therefore  is  approximative  and  suggestive. 

Freshly  made  solutions  of  dextrose  show  bi-rotation  (as 
described  under  lactose).  This  disappears  on  standing  at 
room  temperature  for  24  hours.  It  does  not  occur  with  sirups 
or  the  glucose  used  in  adulterating  sugar-  or  fruit-products, 
but  must  be  borne  in  mind  in  dealing  with  solid  articles. 

The  examination  of  glucose  samples  may  be  conducted  as 
follows : 

Arsenic  may  be  detected  by  Reinsch's  test ;  lead  by  the  routine 
method  given  on  page  58.  The  amount  of  free  acid  is  deter- 
mined by  titration  of  a  known  weight  with  standard  alkali, 
using  phenolphthalein  as  indicator.  Sulfurous  acid  may  be 
detected  by  adding  some  of  the  samples  to  dilute  hydrochloric 
acid,  with  a  few  fragments  of  zinc  in  a  test-tube,  and  covering 
the  mouth  of  the  tube  with  a  piece  of  filter-paper  containing 
some  lead  acetate.  A  spot  of  lead  sulfid  indicates  reducible 
sulfur  compounds.  Calcium  sulphate  or  other  mineral  matter 
may  be  determined  by  the  weight  and  composition  of  the  ash. 


SUGARS  127 

LACTOSE 

Commercial  lactose  is  usually  obtained  from  the  whey  of 
cows'  milk.  Inferior  qualities  contain  notable  amounts  of 
nitrogenous  matter,  mineral  substances,  bacteria,  and  spores 
of  fungi.  Pure  lactose  is  a  white  crystalline  powder,  not 
very  soluble  in  water  and  feebly  sweet.  When  crystalHzed  by 
evaporation  at  low  temperature,  it  retains  one  molecule  of 
water,  but  this  is  easily  removed.  The  freshly  made  solution 
in  water  has  a  dextrorotatory  power  much  greater  than  normal ; 
upon  standing  for  24  hours,  or  immediately  upon  boiling,  it 
acquires  its  normal  rotatory  action.  This  phenomenon, 
known  as  "birotation,"  must  not  be  overlooked  in  examining 
samples  of  lactose  or  concentrated  milk-products.  Lactose 
has  high  reducing  power,  especially  upon  alkaHne  copper 
solutions.  Under  the  influence  of  some  common  organisms 
it  is  rapidly  converted  into  lactic  acid;  by  special  methods  it 
may  be  converted  into  ethyl  alcohol. 

For  qualitative  tests  for  lactose  see  page  in.  Quantitative 
determinations  are  made  either  with  a  polarimeter  or  an 
alkaline  copper  solution.  The  details  of  these  methods  are 
given  in  connection  with  the  analyses  of  milk.  The  examina- 
tion of  commercial  samples  should  be  directed  to  the  deter- 
mination of  the  amount  of  nitrogen,  ash,  lead,  copper,  and 
zinc.  The  sample  should  not  be  acid,  nor  contain  any  appre- 
ciable amount  of  matter  insoluble  in  water. 

MAPLE   SIRUP   AND   MAPLE   SUGAR 

These  are  substantially  sucrose  with  minute  amounts  of 
special  flavors.  Sucrose  from  other  sources  is  often  added- 
Adulteration  with  maple  sirup  glucose  is  also  common.  Much 
attention  has  been  given  to  the  standard  composition  of  pure 
maple  sugar,  in  order  to  determine  adulteration  with  sucrose 
from  other  sources. 

Analytic  methods.     Glucose  is  detected  by  examination  with 


128  FOOD    ANALYSIS 

the  polarimeter  before  and  after  hydrolysis.  Pure  maple 
sugar  is  inverted,  glucose  is  but  slightly  affected.  The  follow- 
ing results  obtained  by  Ogden  illustrate  this : 

Percentage 
Polarimeter  Reading.  Sucrose. 

Direct.         After  Hydrolysis. 

Maple  sirups  free  J 53.1  — 22.2  56.0 

from  glucose :      ( 59.6  — 2 1 .9  60.6 


Maple  sugars: 


{ 


84.1  —28.8  85.9 

88.0  —28.3  87.6 


Maple  sirups  con-  f 80.0  18.9 

taining glucose:  ( loo.o  45.6 

The  methyl  alcohol  method  for  detecting  glucose  in  honey 
will  be  of  some  value.  With  pure  maple  sirup,  the  precipitate 
is  abundant  and  flocculent  but  not  adherent  to  the  glass.  On 
standing,  crystals  of  sucrose  appear.  When  considerable 
glucose  is  present,  a  more  granular  precipitate  appears  which 
adheres  to  the  glass.     For  determination  of  glucose,  see  page  126. 

The  water  in  maple  sirup  is  determined  in  the  usual  way, 
but  it  will  be  advantageous  to  use  a  dilute  liquid  and  spread 
it  over  a  large  surface.  Maple  sirup  should  be  diluted  with  its 
weight  of  water,  and  maple  sugar  dissolved  in  twice  its  weight 
of  water.     The  drying  should  be  completed  in  the  water-oven. 

The  most  important  data  for  judging  of  the  addition  of 
sucrose  are  the  amount  and  alkalinity  of  the  ash,  the  amount  of 
lead  subacetate  precipitate  and  the  malic  acid  value.  Frear,^'' 
who  examined  sirup  and  sugar  made  under  his  own  observation, 
suggests  a  minimum  relation  of  ash  to  sucrose  of  i  to  160,  that 
is,  the  ash  should  not  be  less  than  0.625  ^^  ^^^  total  sucrose. 

The  ash  must  be  determined  with  care,  as  some  of  the  consti- 
tuents are  volatile.  Burning  in  a  muffle  at  as  low  a  tempera- 
ture as  possible  is  preferable.  The  weighing  must  be  done 
promptly,  as  the  ash  is  deliquescent.  In  some  cases,  the  data  of 
alkalinity  of  the  water-soluble  portion  to  phenolphthalein  and 
methyl  orange,  and  the  alkalinity  of  the  insoluble  portion,  will 
be  needed  as  described  on  page  39. 


SUGARS 


129 


@ 


A 


The  lead  subacetate  precipitate  is  measured  by  volume  after 
concentration  by  a  centrifuge,  according  to  the  method  of 
Hortvet.^^  A  special  tube  and  holder,  shown  in  figure  37  on  a 
scale  of  one-half,  is  used.  Each  tube  must  have  a  holder. 
Tubes  and  holders  must  be  closely  balanced  in  pairs,  so  that  the 
centrifuge  will  be  evenly  loaded.  The  holder  may  be  made  of 
soft  wood.  Instrument-makers  can,  however,  make  aluminum 
holders  that  will  be  satisfactory.  The  narrow  part  of  the  tube 
should  be  graduated  in  c.c.  and  fractions. 

5  c.c.  of  sirup  or  5  grams  of  sugar  are  placed  in  the  tube,  10 
c.c.  of  water  added,  and  the  contents  well-mixed,  sugar  being 
allowed  to  dissolve  completely  before  the  final 
mixing.  0.5  c.c.  alumina  cream  and  1.5  c.c. 
of  lead  subacetate  (see  page  118)  are  added, 
the  mixture  again  shaken  and  allowed  to 
stand  for  an  hour,  the  tubes  being  occasion- 
ally rotated  to  facilitate  settling.  Tubes 
must,  of  course,  be  made  up  in  pairs.  They 
are  placed  in  the  centrifuge,  run  for  about 
10,000  turns  within  six  minutes,  and  exam- 
ined ;  any  material  that  may  be  adhering  to 
the  wider  portion  is  loosened  with  wire  at  the 
end,  the  tubes  again  rotated  for  six  minutes, 
and  the  volume  of  the  precipitate  noted,  read- 
ing to  o.oi  c.c.  if  possible.  Each  operator  must  by  trial  with 
samples  of  definite  origin  establish  standards  applicable  to  the 
centrifuge  used.  Using  an  instrument  with  a  radius  of  18.5  cm., 
Hortvet  obtained  with  pure  maple  sirups  1.2  to  2.5  c.c.  and  with 
pure  maple  sugars  1.8  to  4.0  c.c.  Adulterated  articles  give  much 
less.  Experiments  with  pure  sucrose  and  precipitants  must 
be  made  and  the  volume  of  precipitate  noted  as  a  correction. 

The  so-called  ''malic  acid  value,"  of  use  in  judging  the 
quality  of  maple  products,  is  obtained  by  Hortvet's  modifica- 
tion of  the  method  of  Leach  &  Lythgoe.*^ 


Fig.  37. 


130  FOOD   ANALYSIS 

6.7  grams  of  the  sample  are  weighed  into  a  200  c.c.  beaker, 
water  added  to  make  the  volume  20  c.c,  the  solution  made 
slightly  alkaline  with  ammonium  hydroxid,  i  c.c.  of  a  10  per 
cent,  solution  of  calcium  chlorid  and  then  60  c.c.  of  95  per  cent, 
alcohol  added.  The  beaker  is  covered  and  heated  for  one  hour 
on  the  water-bath,  the  heat  withdrawn  and  the  liquid  allowed 
to  stand  overnight.  The  precipitate  is  collected  by  filtering 
through  good  filter  paper  (probably  the  hardened  paper  will 
be  satisfactory),  washed  with  hot  75  per  cent,  alcohol,  until  all 
calcium  chlorid  is  removed,  dried  and  ignited.  20  c.c.  -^ 
hydrochloric  acid  are  added,  the  solution  warmed  until  the 
lime  is  dissolved  and  the  excess  of  acid  determined  by  titration. 
One-tenth  the  number  of  c.c.  of  acid  neutralized  is  the  provi- 
sional malic  acid  value.  With  pure  maple  products  the  figure 
will  not  be  below  0.80. 


HONEY 

Honey  consists  principally  of  dextrose  and  levulose  with 
small  proportions  of  mineral  and  flavoring  matters  and  often 
formic  acid.  In  some  cases  small  amounts  of  sucrose  and 
mannitose  and  a  considerable  proportion  of  carbohydrates  of 
the  dextrin  class  are  present.  Microscopic  examination  will 
usually  show  pollen,  portions  of  insects'  wings,  and  spores  of 
fungi.     Crystallized  dextrose  is  occasionally  present. 

The  color  of  honey  varies  from  light  amber- yellow  to  brown- 
ish-black, according  to  the  source,  and  time  and  manner  of 
storage.  White  clover  honey  is  nearly  colorless.  Strained 
honey  is  that  freed  from  comb  by  straining.  Extracted  honey 
is  freed  from  comb  by  centrifugation  or  settling. 

The  proportion  of  water  ranges  within  the  limits  of  12  and 
22  per  cent.  The  reducing  bodies  calculated  as  dextrose  usu- 
ally amount  to  from  60  to  75  per  cent.  If  sucrose  be  present 
in  but  small  amount  in  the  nectar  of  the  flowers,  it  may  be  en- 


HONEY  131 

tirely  hydrolyzed  in  the  bee  or  after  deposition  in  the  hive,  the 
honey  being  quite  free. 

Honey  contains  no  true  dextrin,  but  many  samples  yield, 
with  strong  alcohol,  precipitates  of  carbohydrate  intermediate 
between  starch  and  sugar,  the  proportion  being  as  high  as  40 
per  cent,  or  more  in  the  case  of  honey  of  coniferous  origin. 

Dextrorotatory  samples,  apparently  pure,  have  been  reported. 
They  were  probably  of  coniferous  origin.     They  have  been 
disregarded  in  the  official  standard. 
U.  S.  Standard. 

Honey  is  the  nectar  and  saccharine  exudation  of  plants, 
gathered,  modified  and  stored  in  the  comb  of  the  honey-bee 
{Apis  mellifica).    It  is  levorotatory. 

Water  should  not  be  over 25.0 

Ash  should  not  be  over 0.25 

Sucrose  should  not  be  over 8.0 

Adulterations. — Bees  are  often  fed  with  cane-sugar,  which 
they  hydrolyze  partially.  Ogden  gives  the  following  results  of 
polarimetric  examination  of  honey  obtained  in  this  way : 

Direct,  i8°.5.     Temperature,  25.2°. 

After  hydrolysis,      — 9.0.     Temperature,  24°. 

The  common  adulterants  of  strained  honey  are  invert-sugar 
and  glucose  sirup.  It  is  usually  impossible  to  detect  with 
certainty  the  addition  of  invert-sugar.  An  ash  higher  than 
0.3  per  cent.,  containing  a  notable  quantity  of  calcium  sul- 
fate, may  point  to  invert-sugar  or  to  glucose  sirup.  Samples 
are  frequently  encountered  which  give  a  direct  polarimetric 
reading  of  — 14  to  — 20  on  the  cane-sugar  scale,  and,  after 
inversion,  slightly  higher  figures ;  these  in  many  cases  probably 
contain  added  invert-sugar. 

The  direct  addition  of  sucrose  to  honey  is  not  usual,  but 
has  been  practised  in  some  cases.  Its  presence  in  considerable 
quantity  will  be  indicated  by  the  high  right-handed  rotation, 


132  FOOD   ANALYSIS 

decidedly  reduced  on  hydrolysis.  A  sample  of  so-called  "hoar- 
hound  honey"  examined  in  the  chemical  laboratory  of  the 
U.  S.  Department  of  Agriculture  was  found  to  consist  mainly 
of  a  solution  of  sucrose  with  some  alcohol. 

A  common  method  of  adulteration  consists  in  pouring 
glucose  sirup  over  honeycomb  from  which  the  honey  has 
been  drained,  and  allowing  the  mixture  to  stand  until  it  has 
acquired  a  honey  flavor.  Such  samples  give  a  high  positive 
polarimetric  reading,  but  little  affected  by  hydrolysis. 

Dextrin  is  a  constant  constituent  of  commercial  glucose 
sirup,  and  the  attempt  has  been  made  to  detect  the  latter  by 
the  formation  of  a  precipitate  when  the  sample  is  diluted  with 
alcohol.  It  has  been  shown,  however,  that  many  samples  of 
honey  contain  a  considerable  material  precipitable  by  ethyl 
alcohol,  amounting  in  some  instances  to  50  per  cent.  Accord- 
ing to  Beckmann,  better  results  may  be  obtained  by  the  use 
of  methyl  alcohol.  Pure  honey,  both  the  ordinary  form  and 
the  dextrorotatory  variety,  that  might  be  regarded  as  adul- 
terated with  glucose,  was  found  to  yield,  when  largely  diluted 
with  methyl  alcohol,  only  a  slight  flocculent  precipitate,  which 
did  not  adhere  to  the  walls  of  the  vessel.  Glucose  sirup 
yielded  a  precipitate  of  dextrin  amounting  to  about  31  per 
cent.,  which  produced  with  a  solution  of  iodin  in  potassium 
iodid  the  red  characteristic  of  erythrodextrin.  The  reaction 
is  also  obtained  by  direct  addition  of  the  iodin  solution  to 
honey  containing  glucose  sirup.  The  quantitative  determina- 
tion is  made  by  diluting  8  grams  of  the  sample  with  8  c.c.  of 
water  and  diluting  the  mixture  to  100  c.c.  with  methyl  alcohol. 
The  precipitate  is  filtered  off,  washed  with  methyl  alcohol, 
dissolved  in  water,  and  the  solution  evaporated  on  the  water- 
bath  with  repeated  addition  of  methyl  alcohol  until  quite  dry. 
Adulteration  with  solid  glucose  (so-called  grape-sugar)  cannot 
be  detected  by  this  method,  since  in  the  preparation  of  this 
the  hydrolysis  is  carried  further.  Methyl  alcohol  produces  only 
a  slight  turbidity. 


HONEY  133 

Beckmann  has  also  proposed  the  following  test  for  solid 
glucose  and  glucose  sirup:  5  c.c.  of  the  honey  solution  (20 
grams  in  100  c.c.  of  water)  are  mixed  with  3  c.c.  of  a  2  per 
cent,  solution  of  barium  hydroxid,  17  c.c.  of  methyl  alcohol 
added,  and  the  mixture  shaken.  Pure  honey  remains  clear, 
but  in  the  presence  of  dextrin,  glucose,  or  glucose  sirup  a 
considerable  precipitate  is  formed.  The  test  was  applied 
quantitatively  by  increasing  the  amount  taken  to  50  grams, 
the  methyl  alcohol  added  rapidly  to  avoid  deposition  on  the 
glass,  the  liquid  well  shaken  once^  the  precipitate  collected  on 
a  tared  asbestos  filter,  washed  with  methyl  alcohol  and  ether, 
and  dried  at  55°  to  60°.  Excessive  shaking  was  avoided  in 
order  to  prevent  the  action  of  air  on  precipitate.  It  was  found 
that  the  quicker  the  working,  the  more  accurate  the  results. 
In  some  cases  it  was  found  necessary  to  determine  the  sulfates 
and  phosphates  and  to  correct  the  results  accordingly.  The 
mean  results  in  test  analyses,  calculated  to  i  gram  of  the 
material  taken,  were:  Dextrin,  0.916  gram;  glucose  sirup, 
0.455  gram;  solid  glucose,  0.158  gram.  Admixture  of  dex- 
trorotatory conifer  honey  to  the  extent  of  90  per  cent,  was  not 
found  to  increase  the  amount  of  precipitate,  but,  on  the  con- 
trary, to  diminish  it  slightly. 

The  following  are  results  obtained  on  samples  of  natural 
honey  rich  in  dextrinous  bodies.  Sp.  is  the  specific  rotatory 
power  for  yellow  light : 

Apple  honey, Sp.  =  — 12.2.     Precipitate  by  ethyl  alcohol  23.7  per  cent. 

Barium  precipitate  5  c.c.  10  per  cent,  solution  gave  0.0044  gram. 
"  "  5  c.c.  20  per  cent.        "  "   0.0072     " 

Umbellifer  honey, Sp.  =    — 4.6.     Precipitate  by  ethyl  alcohol  29.1  per  cent. 

Barium  precipitate  5  c.c.  10  per  cent,  solution  gave  0.0148  gram. 
"  "  5  c.c.  20  per  cent.        "  "   0.023       " 

Conifer  honey, Sp.  =      16.9.     Precipitate  by  ethyl  alcohol  41 .9  per  cent. 

Barium  precipitate  5  c.c.  10  per  cent,  solution  gave  0.0132  gram. 
"  "         5  c.c.  20  per  cent.        "  "   0.0248     " 

It  appears  from  these  data  that  even  under  unfavorable  cir- 


134  FOOD   ANALYSIS 

cumstances  it  is  possible  to  recognize  the  addition  of  from  5 
to  10  per  cent,  of  ordinary  dextrin,  10  to  20  per  cent,  of  glucose 
sirup,  and  30  to  40  per  cent,  of  solid  glucose  to  conifer  contain- 
ing as  much  as  40  per  cent,  of  natural  dextrinous  matter.  With 
ordinary  samples,  such  as  the  apple  honey  just  noted,  adultera- 
tion would  be  much  more  easily  detected. 

For  the  determination  of  glucose  Leach  ^^  recommends  hy- 
drolyzing  in  the  usual  manner,  taking  the  reading  at  87°  (see 
page  17)  and  dividing  by  175.  The  quotient  is  the  approximate 
percentage  of  glucose.     (See  page  126.) 

Konig  and  Karsch  have  proposed  the  following  method  for 
detection  of  glucose :  40  grams  of  the  sample  are  made  up  to 
40  c.c.  with  water,  well  mixed,  20  c.c.  placed  in  a  250  c.c.  flask, 
and  absolute  alcohol  added,  by  very  small  portions  at  a  time, 
with  constant  shaking,  until  the  flask  is  filled  to  the  mark. 
The  mixture  is  allowed  to  stand  for  several  days  with  occasional 
shaking.  The  solution  is  again  shaken  well  and  quickly 
filtered.  100  c.c.  of  the  filtrate  are  evaporated  to  remove 
alcohol,  but  not  to  dryness,  the  residue  made  up  to  20  c.c.  by 
addition  of  lead  subacetate  and  water,  the  solution  filtered  and 
examined  in  the  polarimeter. 

The  precipitate  produced  by  alcohol  is  washed  several 
times  with  90  per  cent,  alcohol  and  then  dissolved  off  the 
filter  with  water,  evaporated  on  the  water-bath,  dried  in  the 
water-oven,  and  weighed. 

The  following  are  some  of  the  results  obtained : 


Percentage  of  Reduc- 

POLARIMETRIC  READING. 

ing  Carbohydrates 

Before  Treatment 

After  Treatment 

Precipitated  by 

with  Alcohol. 

with  Alcohol. 

Alcohol. 

Pure  honey, 

....      -6.4 

-8.5 

3-2 

—12.4 

134 

1-7 

-16.7 

17.0 

—117 

ir.7 

3-3 

—9.2 

13.2 

—7.7 

9.9 

9-7 

—9.9 

12.5 

— 

—7.5 

6.2 

34.0 

Honey    containing     75 

per 

cent,  glucose, 

....       25.5 

2.4 

20.6 

CANDIES  AND  CONFECTIONS  1 35 

Molasses  is  said  to  have  been  added  to  honey,  but  its  use 
is  infrequent.  The  ash  of  molasses  is  high  and  contains 
considerable  chlorids.  Beckmann  suggests  its  detection  by 
the  production  of  a  precipitate  on  addition  of  a  solution  of  lead 
subacetate  in  methyl  alcohol,  the  formation  of  which  is  at- 
tributed to  the  presence  of  raffinose.  5  grams  of  the  solution 
are  mixed  with  22.5  c.c.  of  methyl  alcohol  and  5  c.c.  of  a  solu- 
tion of  the  honey  (which  should  not  contain  more  than  25  per 
cent.)  are  added.  If  the  honey  be  pure,  the  solution  will  re- 
main clear,  but  in  the  presence  of  molasses  a  precipitate  will  be 
formed.  The  amount  of  precipitate  varies  according  to  the 
particular  sample  of  molasses  present,  but  Beckmann  claims 
that  it  will  usually  be  possible  to  detect  as  low  as  10  per  cent. 

CANDIES   AND   CONFECTIONS 

These  terms  include  many  articles,  some  complex  mixtures, 
the  composition  of  which  is  secret.  The  main  ingredient  is 
usually  sucrose,  but  invert-sugar,  dextrose,  starch,  mucilaginous 
substances,  gelatin,  colors,  and  flavors  are  largely  employed. 
Among  the  objectionable  ingredients  are  paraffin,  clay,  calcium 
sulfate,  mineral  colors,  fusel  oil,  and  metal  foil.  Preservatives 
are  usually  unnecessary.  The  use  of  mineral  colors  has  declined 
much  of  late  years,  owing  to  the  cheapness  and  superior  brilli- 
ancy of  artificial  organic  dyes,  but  some  of  the  chocolate  con- 
fections contain  considerable  amounts  of  brown  ferric  hydroxid. 

The  plain  candies,  such  as  rock  candy,  molasses  candy,  and 
candy  toys  are  usually  only  crystallized  or  melted  sucrose 
with  flavors  and  colors.  Actual  experiment  by  manufacturing 
confectioners  has  furnished  the  following  data  for  proportion 
of  color: 

One  part  of  auramin  will  color  30,000  parts  of  melted  sucrose 
to  the  deepest  yellow  required.  One  part  of  eosin  or  fluores- 
cein will  give  the  average  tint  to  28,000  parts  of  "cream  goods" 
(such  as  used  in  high-class  "mixtures")  or  21,000  parts  of 


136  FOOD   ANALYSIS 

clear  and  hard  candies,  or  12,000  to  24,000  parts  of  some  other 
types.  These  figures  are  for  "soUd"  coloring — that  is,  the 
whole  mass  is  dyed;  when  merely  surface-coloring  is  done,  the 
quantity  needed  is  about  i  part  to  50,000. 

The  ash  of  candies  and  confections  is  generally  below  one 
per  cent.  The  flavors  are  often  artificial.  A  brand  called 
*'Rock  and  Rye  Drops"  is  often  flavored  with  fusel  oil. 

The  colors  employed  are  numerous  and  constantly  chang- 
ing. At  present  various  eosins  {e.  g.,  rhodamin  B,  rose  bengale, 
erythrosin)  are  much  used  for  red,  fluorescein  and  auramin  for 
yellow,  malachite  green  and  sulfonated  allies  for  green.  Cochi- 
neal and  vegetable  colors,  such  as  chlorophyl,  cudbear  and 
fustic,  have  come  largely  into  use  of  late.  Bismarck  brown  is 
apt  to  be  employed  in  chocolate  colors. 

Analytic  Methods. — The  examination  of  candies  will  be 
usually  limited  to  identification  of  the  coloring-matters  and 
detection  of  starch,  clay,  calcium  sulfate,  paraffin,  and  poison- 
ous metals.  Determinations  of  sucrose,  invert-sugar,  dextrose, 
and  gum  are  difficult  and  of  no  practical  interest. 

Glucose  may  be  detected  and  approximately  determined  as 
in  honey  and  maple  sugar. 

A  weighed  portion  of  the  sample  is  stirred  in  cold  water 
until  all  soluble  matter  is  taken  up,  the  liquid  is  filtered  in  a 
Gooch  crucible,  the  residue  washed  with  cold  water,  trans- 
ferred to  the  crucible,  dried  at  a  low  heat,  weighed,  burnt  off, 
and  again  weighed.  The  figures  for  insoluble  residue  and 
ash  will  be  obtained.  The  aqueous  solution  will  usually 
contain  the  coloring  and  some  of  the  flavoring  material;  the 
former  may  often  be  identified  by  the  tests  given  on  pages  64  to 
75.  Many  flavoring  agents  may  be  recognized  by  odor.  If 
a  moderately  large  sample  is  dissolved,  fractional  distillation  as 
described  in  connection  with  fruit  juices  may  give  information. 
Starch  may  be  detected  by  iodin.  Any  notable  amount  of 
gelatin  or  albumin  will  be  indicated  by  the  Kjeldahl  method. 
Clay,  calcium  sulfate  and  iron  oxid  will  be  found  in  the  ash. 


FATS  AND  OILS  137 

FATS  AND  OILS 

The  methods  for  determining  melting  and  solidifying  points 
and  specific  gravity  of  fats  and  oils  have  been  fully  described 
in  the  introductory  part.  Some  comparative  data  are  given 
in  this  section,  together  with  methods  applied  almost  exclu- 
sively to  this  class  of  food-products. 

Specific  gravity  determined  at  temperatures  other  than 
15.5°  may  be  reduced  to  this  by  a  correction  of  0.00064  for 
each  degree.  This  figure  is  derived  from  results  obtained  by 
Allen.  The  specific  gravity  of  fats  and  oils  changes  by  time. 
The  follov^ing  table,  due  to  Thomson  &  Ballentyne,  shows  this 
fact ;  the  figures  are  for  -J^^ : 


One  Month. 

Three  Months. 

Six  Months. 

0.9187 

0.9208 

0.9246 

0.9237 

0.9261 

0.9320 

0.9213 

0.9233 

0.9267 

0.9183 

0.9188 

0.9207 

Olive, .0.9168 

Cottonseed, 0.9225 

Arachis, 0.9209 

Rape, 0.9168 

Color-tests. — Many  color-tests  for  oils  and  fats  have  been 
proposed.  The  reactions  are  in  some  cases  dependent  on 
natural  impurities  and  may  fail  when  the  sample  has  been  pro- 
duced under  unusual  conditions  or  subjected  to  special  treat- 
ment. Thus,  cottonseed  oil  by  heating  loses  susceptibility 
to  several  color-tests,  while  lard  derived  from  animals  fed 
liberally  on  cottonseed  products  will  give  distinctly  the  cotton- 
seed oil  reactions.  Special  color-tests  applicable  to  particular 
oils  or  fats  will  be  described  in  connection  with  these.  The 
following  general  reactions  are  much  used : 

Sulfuric  Acid  Test. — A  drop  or  two  of  strong  sulfuric 
acid  is  placed  in  the  center  of  about  20  drops  of  oil,  allowed 
to  rest  a  few  moments,  the  color  change  noted,  the  mixture 
stirred,  and  the  effect  again  noted.  The  charring  action  which 
often  obscures  the  reaction  may  be  avoided  by  dissolving  a 
13 


138 


FOOD   ANALYSIS 


drop  of  the  oil  in  20  drops  of  carbon  disulfid  and  agitating 
this  with  the  sulfuric  acid. 

Nitric  Acid  Test. — Bach's  method  is  to  agitate  5  c.c.  of 
the  sample  with  5  c.c.  of  nitric  acid,  sp.  gr.  1.30.  The  color 
reaction  is  noted,  the  mixture  immersed  in  boiHng  water  for 
5  minutes,  and  the  condition  again  noted.  The  reaction  may 
be  violent,  and  care  must  be  taken  to  protect  persons  and 
apparatus  against  injury. 

Massie's  method  is  to  agitate  10  grams  with  5  c.c.  of  nitric 
acid,  sp.  gr.  1.40,  and  note  the  color  at  the  end  of  one  hour. 

Lewkowitsch  states  that  an  acid  of  specific  gravity  1.375 
is  preferable.  In  some  cases  the  mixture  should  stand  24  hours 
before  the  final  observation  is  made. 

Mixtures  of  strong  sulfuric  acid  and  strong  nitric  acid  have 
been  used,  but  the  results  are  not  of  material  use  with  food  oils. 

The  following  data,  compiled  by  Allen,  will  illustrate  the 
value  of  these  color- tests : 


Olive, 

Cotton- 
seed. 

Sesame. 

Arachis. 

Rape. 

Sulfuric  Acid.— 

Before  stirring,  . 

Yellow- 

Red-brown. 

Yellow    to 

Yellow 

green 

orange. 

with 

or  brown. 

red  rings. 

After  stirring,    . 

Brown  or 

Dark    red- 

Green      or 

Brown. 

green. 

brown. 

brown. 

Nitric  Acid.— 

Bach's  test : 

After  agitation 

Pale- 
green. 

Yellow- 
brown. 

White. 

Pale  rose. 

Pale  rose. 

After  heating, 

Orange- 

Red-brown. 

Brown- 

Brown- 

Orange- 

yellow. 

yellow. 

yellow. 

yellow. 

After  1 2  hours' 

standing,    . 

Solid. 

Buttery. 

Liquid. 

Solid. 

Solid. 

Massie's  test,     . 

Yellow- 
green. 

Orange-red 

Yellow- 
orange. 

Pale  red. 

Orange. 

Time  for  solidifica- 

tion (minutes),  . 

60 

105 

105 

200 

FATS   AND  OILS  1 39 

lodin  Number. — This,  also  called  iodin  value,  is  the  per- 
centage of  iodin  absorbed  under  specified  conditions.  Baron 
Hiibl  discovered  that  a  solution  of  iodin  and  mercuric  chlorid 
is  more  uniform  in  action  than  iodin  alone,  and  this  solution, 
commonly  known  as  Hiibl's  reagent,  is  usually  employed. 
The  following  reagents  are  used  in  the  process : 

Iodin  solution.  25  grams  of  iodin  are  dissolved  in  500  c.c. 
of  95  per  cent,  alcohol. 

Mercuric  chlorid  solution.  25  grams  of  mercuric  chlorid 
solution  are  dissolved  in  500  c.c.  of  95  per  cent,  alcohol  and 
the  solution  filtered,  if  necessary. 

Starch  solution.     See  page  56.  • 

Potassium  iodid  solution.     15  grams  in  100  c.c.  of  water. 

Potassium  die hr ornate  solution.  3.874  grams  of  pure  potas- 
sium dichromate  in  1000  c.c.  of  water. 

For  use,  equal  parts  of  the  iodin  and  mercuric  chlorid  solu- 
tions are  mixed  and  allowed  to  stand  at  least  12  hours. 

The  strength  of  the  thiosulfate  solution  is  determined  as 
follows:  20  c.c.  of  potassium  dichromate  solution,  10  c.c.  of 
potassium  iodid  solution,  and  5  c.c.  of  strong  hydrochloric  acid 
are  mixed  in  a  glass-stoppered  flask,  and  the  solution  of  sodium 
thiosulfate  is  allowed  to  flow  in  from  a  buret  until  the  yellow 
color  of  the  mixture  has  almost  disappeared.  A  few  drops 
of  starch  solution  are  then  put  in  and  the  addition  of  the  thio- 
sulfate continued  until  the  blue  color  just  appears.  The  num- 
ber of  cubic  centimeters  of  thiosulfate  solution  used,  multiplied 
by  5,  is  equivalent  to  i  gram  of  iodin. 

Not  more  than  i  gram  of  fat  is  weighed  in  a  glass-stoppered 
flask  holding  about  300  c.c,  and  10  c.c.  of  chloroform  or  carbon 
tetrachlorid  are  added.  After  complete  solution  30  c.c.  of  the 
iodin  solution  are  added  and  the  flask  is  placed  in  the  dark  for 
three  hours,  with  occasional  shaking.  20  c.c.  of  potassium 
iodid  solution  and  100  c.c.  of  water  are  added  to  the  contents  of 
the  flask.     Any  iodin  which  may  be  noticed  upon  the  stopper  of 


I40  FOOD   ANALYSIS 

the  flask  should  be  washed  back  into  the  flask  with  the  potas- 
sium iodid  solution.  The  excess  of  iodin  is  now  titrated  with 
the  sodium  thiosulfate  solution,  which  is  run  in  gradually, 
with  constant  shaking,  until  the  yellow  color  of  the  solution 
has  almost  disappeared.  A  few  drops  of  starch-paste  are 
added,  and  the  titration  continued  until  the  blue  color  has 
entirely  disappeared.  Toward  the  end  of  the  reaction  the 
flask  should  be  closed  and  violently  shaken,  so  that  iodin 
remaining  in  the  chloroform  may  be  taken  up  by  the  potassium 
iodid  solution.  A  sufficient  quantity  of  sodium  thiosulfate 
solution  should  be  added  to  prevent  a  reappearance  of  any 
blue  color  in  the  flask  for  five  minutes. 

At  the  time  of  adding  the  iodin  solution  to  the  fats,Hwo 
flasks  of  the  same  size  as  those  used  for  the  determination 
should  be  employed  for  conducting  the  operation  without  fat. 
In  every  other  respect  the  performance  of  the  blank  experi- 
ments should  be  just  as  described.  These  blank  experiments 
must  be  made  each  time  the  iodin  solution  is  used. 

Iodin  monobromid,  used  as  suggested  by  Hanus,^^  is  a  satis- 
factory substitute  for  Hiibl's  solution.  It  is  prepared  by  dis- 
solving 13  grams  of  iodin  in  a  liter  of  glacial  acetic  acid  and 
adding  3  c.c.  bromin,  by  which  the  halogen  content  is  doubled. 
The  acetic  acid  must  be  free  from  substances  that  reduce  a 
mixture  of  chromic  and  sulfuric  acids.  The  iodin  mono- 
bromid keeps  for  several  months  and  the  maximum  absorption 
occurs  in  30  minutes,  but  oils  of  high  iodin  number  should  be 
given  an  hour.  The  solution  is  used  similarly  to  that  of  Hiibl, 
except  that  an  excess  of  at  least  70  per  cent,  of  unabsorbed 
iodin  is  necessary,  and  only  10  c.c.  of  the  potassium  iodid  solu- 
tion are  added,  the  solutions  being  well  mixed  before  the  dilut- 
ing water  is  added. 

Especial  care  is  needed  in  measuring  the  solution,  as  the  co- 
efficient of  expansion  of  acetic  acid  is  high  and  slight  changes  in 
temperature  will  cause  appreciable  errors. 


FATS   AND   OILS 


141 


loDiN  Number  of  Liquid  Acids. — This  determination  is 
sometimes  of  value  for  detection  of  admixture  of  vegetable 
oils  vv^ith  animal  oils.  The  separation  of  the  oleic  and  other 
liquid  fatty  acids  is  best  made  by  the  method  of  Muter  &  De 
Koningh,  as  follows : 

3  grams  of  the  fat  are  mixed  with  50  c.c.  of  alcohol  and  a 
fragment  of  potassium  hydroxid  in  a  flask  furnished  with  a 
long  tube.  The  mixture  is  boiled  until  saponi- 
fication is  complete,  when  a  drop  of  phenol- 
phthalein  solution  is  added  and  acetic  acid  until 
the  solution  is  slightly  acid.  AlcohoHc  solution 
of  potassium  hydroxid  is  added  drop  by  drop 
until  *a  faint  permanent  pink  tint  is  obtained, 
when  the  liquid  is  poured  slowly,  with  constant 
stirring,  into  a  beaker  containing  a  boiling  solu- 
tion of  3  grams  of  neutral  lead  acetate  in  200  c.c. 
of  water.  The  solution  is  rapidly  cooled  and 
stirred  at  the  same  time,  and,  when  cold,  the 
clear  liquid  is  poured  off.  The  precipitate  is 
well  washed  with  boiling  water  by  decantation, 
transferred  to  a  stoppered  bottle,  mixed  with  120 
c.c.  of  ether,  and  allowed  to  remain  12  hours. 
Wallenstein  &  Finck  use  a  Drechsel  gas- 
washing  flask  having  the  tube  shortened  about 
two-thirds,  to  contain  the  ethereal  solution,  and 
pass  a  current  of  hydrogen  through  it  for  about 
a  minute.  In  the  case  of  white  fats  the  liquid  is 
said  to  remain  colorless  at  the  end  of  12  hours,  but  if  free  access 
of  air  is  permitted,  a  dark-yellow  solution  is  produced  by  oxida- 
tion. Lead  oleate,  hypogeate,  linolate,  or  ricinolate  will  be  dis- 
solved by  the  ether,  leaving  lead  laurate,  myristate,  palmitate, 
stearate,  and  arachidate  undissolved.  Lead  erucate  is  sparingly 
soluble  in  cold  ether,  but  readily  in  hot.  The  contents  of  the 
bottle  are  filtered  through  a  covered  filter  into  a  Muter  separating- 


FlG.  38. 


142  FOOD   ANALYSIS 

tube  (Fig.  38),  40  c.c.  of  dilute  hydrochloric  acid  (1:4)  added, 
and  the  tube  shaken  until  the  clearing  of  the  ethereal  solution 
shows  that  the  decomposition  of  the  lead  soaps  is  complete.  The 
aqueous  Hquid,  containing  lead  chlorid  and  excess  of  hydro- 
chloric acid,  is  run  off  through  the  bottom  tap,  water  added, 
and  agitated  with  the  ether  and  the  process  of  washing  by 
agitation  repeated  until  the  removal  of  the  acid  is  complete. 
Water  is  then  added  to  the  zero  mark  and  sufficient  ether  to 
bring  the  ether  to  a  definite  volume  (e.  g.,  200  c.c).  An 
aliquot  portion  of  this  (e.  g.,  50  c.c.)  is  then  removed  through  the 
side  tap  and  the  residue  weighed  after  evaporation  of  the  ether 
in  a  current  of  carbon  dioxid.  Another  aliquot  portion  of  the 
ethereal  solution  should  be  distilled  to  a  small  bulk  (avoiding 
complete  evaporation),  alcohol  added,  and  the  solution  titrated 
with  decinormal  sodium  hydroxid  and  phenolphthalein  or 
methyl-orange,  from  which  the  fatty  acids  may  be  calculated 
from  the  result,  or  their  mean  combining  weight  deduced  there- 
from. A  third  aliquot  part  of  the  ethereal  solution  should  be 
evaporated  at  about  60°  in  a  flask  traversed  by  a  rapid  stream 
of  dry  carbon  dioxid.  When  eyery  trace  of  ether  is  removed, 
50  c.c.  of  the  iodin- mercuric  chlorid  solution  (p.  139)  should  be 
added,  the  stopper  inserted,  and  the  liquid  kept  in  absolute 
darkness  for  12  hours,  after  which  an  excess  of  potassium  iodid 
solution  is  added  and  250  c.c.  of  water,  and  the  excess  of  iodin 
ascertained  with  thiosulfate  solution  in  the  usual  way.  From 
the  result  the  iodin  number  is  calculated.  The  Hanus  method 
may  be  used  instead  of  the  Hiibl  method. 

Volatile  Acids. — This  method  was  first  suggested  by  Hehner 
&  AngelV^but  was  systematized  by  Reichert,^^and  hence  is  gen- 
erally called  the  Reichert  process.  In  this  form  it  is  carried 
out  by  saponifying  2.5  grams  of  the  fat,  adding  excess  of  sulfuric 
acid,  distilling  a  definite  portion  of  the  liquid,  and  titrating  the 
distillate  with  ^  alkali.  The  number  of  cubic  centimeters  of 
this  solution  required  to  overcome  the  acidity  of  the  distillate 


FATS  AND  OILS  1 43 

is  called  the  Reichert  number.  E.  MeissP^  suggested  the  use  of  5 
grams,  and  the  number  so  obtained  is  called  the  Reichert- 
Meissl  number.  Alcoholic  solution  of  potassium  hydroxid  was 
originally  used  for  saponification,  but  the  solution  devised  by 
Leffmann  &  Beam,"  namely,  sodium  hydroxid  in  glycerol,  is 
more  satisfactory.     The  reagents  and  operation  are  as  follows : 

Glycerol-soda. — 100  grams  of  pure  sodium  hydroxid  are 
dissolved  in  100  c.c.  of  distilled  water  and  allowed  to  stand 
until  clear.  20  c.c.  of  this  solution  are  mixed  with  180  c.c. 
of  pure  concentrated  glycerol.  The  mixture  can  be  conveni- 
ently kept  in  a  capped  bottle  holding  a  10  c.c.  pipet,  with  a 
wide  outlet. 

Suljuric  Acid. — 20  c.c.  of  pure  concentrated  sulfuric  acid, 
made  up  with  distilled  water  to  100  c.c. 

Sodium  Hydroxid. — An  approximately  decinormal,  accu- 
rately standardized,  solution  of  sodium  hydroxid. 

Indicator. — Solution  of  phenolphthalein  or  methyl-orange. 

A  300  c.c.  flask  is  washed  thoroughly,  rinsed  with  alcohol  and 
then  with  ether,  and  thoroughly  dried  by  heating  in  the  water- 
oven.  After  cooling,  it  is  allowed  to  stand  for  about  15  minutes 
and  weighed.  (In  ordinary  operation  this  preparation  of  the 
flask  may  be  omitted.)  A  pipet,  graduated  to  5.75  c.c,  is 
heated  to  about  60°  and  filled  to  the  mark  with  the  well- mixed 
fat,  which  is  then  run  into  the  flask.  After  standing  for  about 
15  minutes  the  flask  and  contents  are  weighed.  20  c.c.  of  the 
glycerol-soda  are  added  and  the  flask  heated  over  the  Bunsen 
burner.  The  mixture  may  foam  somewhat;  this  may  be  con- 
trolled, and  the  operation  hastened  by  shaking  the  flask.  When 
all  the  water  has  been  driven  off,  the  liquid  will  cease  to  boil, 
and  if  the  heat  and  agitation  be  continued  for  a  few  moments, 
complete  saponification  will  be  effected,  the  mass  becoming 
clear.  The  whole  operation,  exclusive  of  weighing  the  fat, 
requires  about  five  minutes.  The  flask  is  withdrawn  from  the 
heat  and  the  soap  dissolved  in  135  c.c.  of  water.    The  first 


144 


FOOD   ANALYSIS 


portions  of  water  should  be  added  drop  by  drop,  and  the  flask 
shaken  between  each  addition  in  order  to  avoid  foaming. 
When  the  soap  is  dissolved,  5  c.c.  of  the  dilute  sulfuric  acid  are 
added,  a  piece  of  pumice  dropped  in,  and  the  liquid  distilled 
until  no  c.c.  have  been  collected.  The  condensing  tube  should 
be  of  glass,  and  the  distillation  conducted  at  such  a  rate  that 
the  above  amount  of  distillate  is  collected  in  30  minutes. 

The  distillate  is  usually  clear;    if  not,  it  should  be  thor- 
oughly mixed,  filtered  through  a  dry  filter,  and  100  c.c.  of 


.^^ 


Fig.  39. 


the  filtrate  taken.  A  little  of  the  indicator  is  added  to  the 
distillate,  and  the  standard  alkali  run  in  from  a  buret  until 
neutralization  is  attained.  If  only  100  c.c.  of  the  distillate 
have  been  used  for  the  titration,  the  number  of  cubic  centi- 
meters of  alkali  should  be  increased  by  one-tenth. 

The  distilling  apparatus  shown  in  figure  39  is  that  recom- 
mended by  the  A.  O.  A.  C.  (and  since  adopted  in  Great  Britain), 
and  the  directions  for  preparing  the  flask  are  also  from  the 
same  source,  but  when  it  is  intended  merely  to  distinguish 


FATS   AND   OILS  I45 

butter  from  oleomargarin,  it  will  be  sufficient  to  measure  into  a 
flask  3  or  6  c.c.  of  the  clear  fat,  and  operate  upon  this  directly 
in  an  ordinary  distilling  apparatus. 

A  blank  experiment  should  be  made  to  determine  the  amount 
of  standard  alkali  required  by  the  materials  employed.  With 
a  good  quality  of  glycerol,  this  will  not  exceed  0.5  c.c. 

Most  fats  give  distillates  containing  but  little  acid. 

Saponification  Value. — Koettstorfer  Number. — This  is 
the  number  of  milligrams  of  potassium  hydroxid  required  for 
the  saponification  of  i  gram  of  fat.  Its  use  was  suggested 
by  Berthelot,  and  it  was  applied  to  the  examination  of  butter 
by  Koettstorfer.^^  If  the  saponification  value  be  divided  by  lo, 
the  result  will  be  the  percentage  of  alkali  required  for  saponi- 
fication.    The  reagents  and  process  are  as  follows: 

Alcoholic  potassium  hydroxid.  40  grams  of  good  potassium 
hydroxid  are  dissolved  in  sufficient  alcohol  to  make  1000 
c.c.  The  solution  should  be  clear  and  light  yellow.  Alcohol 
that  becomes  brown  is  unfit  for  use. 

Purified  methyl  alcohol  and  sodium  hydroxid  may  be  sub- 
stituted. The  saponification  value  of  sodium  hydroxid  may  be 
converted  into  the  standard  number  by  multiplying  by  1.4. 

Halj-normal  hydrochloric  acid  accurately  standardized. 

Phenol phthalein  solution. 

The  process  is  as  follows:  About  1.5  grams  of  the  sample 
are  accurately  weighed  into  a  small  flask,  25  c.c.  of  the  alcoholic 
alkali  added,  and  the  mass  saponified.  The  same  amount  of 
the  alkaline  solution  must  be  used  in  all  comparative  experi- 
ments, and  it  must  be  accurately  measured.  The  flask  is 
provided  with  an  inverted  condenser  or,  more  simply,  with  a 
tube  about  50  cm.  long  and  0.5  cm.  caliber  passing  through 
the  cork.  It  is  heated  on  the  water-bath  for  30  minutes, 
being  occasionally  given  a  rotatory  motion.  The  alcohol 
should  not  boil  actively.  A  drop  of  the  indicator  solution  is 
added,  the  liquid  allowed  to  cool  somewhat,  the  flask  being 


146 


FOOD   ANALYSIS 


closed,  and  then  titrated  with  the  standard  acid.  A  blank  test 
should  be  made,  which  will  eliminate  some  of  the  errors  of 
experiment.  The  number  of  cubic  centimeters  used  for  titra- 
tion of  the  saponified  mass,  subtracted  from  the  number  used 
in  the  blank  experiment,  will  give  the  acid  corresponding  to  the 
alkali  which  has  been  neutralized  by  the  fat.  From  this,  the 
amount  of  alkali  can  be  determined  and  calculated  by  simple 
proportion  to  i  gram  of  fat. 

Flasks  of  the  same  kind  of  glass  should  be  used  in  com- 
parative experiments,  as  some  of  the  cheaper  forms  of  glass 

are  notably  affected  by  alkali.  A 
special  form  of  saponification  flask 
and  method  of  heating  used  by  the 
A.  O.  A.  C.  are  shown  in  figure  40. 
The  flask  is  arranged  so  that  the 
cork  can  be  tied  down. 

Allen  suggested  the  use  of   the 
figure  representing  the  grams  of  fat 
saponified  by  1000  c.c.  of  normal 
alkali.      This     would    render    the 
method  independent  of  the  alkali 
employed,  but  the  suggestion    has 
not  been  generally  followed.     The 
datum  was  called  by  Allen  saponi- 
fication equivalent.     It  may  be  ob- 
tained in  any  case  by  dividing  56100  by  the   saponification 
number.    Similarly,  the  saponification  number  may  be  obtained 
by  dividing  56100  by  the  saponification  equivalent. 

Acid  Value. — This  is  the  amount  of  free  fatty  acid.  The 
reagents  required  are  ^  sodium  hydroxid  and  neutral  alcohol. 
The  latter  is  prepared  by  adding  to  a  good  quality  of  alcohol 
a  drop  or  two  of  phenolphthalein  solution  and  sodium  hydroxid 
drop  by  drop  with  stirring  until  the  color  change  occurs.  10 
grams  of  the  sample  are  placed  in  a  bottle  provided  with  a  glass 


Fig.  40. 


FATS   AND   OILS  1 47 

stopper,  about  50  c.c.  of  the  neutral  alcohol  and  i  c.c.  of  phenol- 
phthalein  solution  added,  and  the  mass  heated  to  boiling  by 
immersing  the  bottle  in  hot  water.  The  bottle  is  then  stoppered 
and  well  agitated  and  the  liquid  titrated  with  standard  alkali, 
the  bottle  being  vigorously  shaken  after  each  addition  until  a 
faint  pink  coloration  persists  for  a  minute  or  two.  On  long 
standing  the  alkali  acts  upon  the  fat  itself,  i  c.c.  of  -^  alkali  is 
equivalent  to  0.0256  gram  of  palmitic  acid,  0.0284  gram  of 
stearic  acid,  or  0.0282  gram  of  oleic  acid.  As  the  acid  present 
may  not  be  known,  it  is  usual  to  express  the  result  as  the 
milligrams  of  potassium  hydroxid  required  to  neutralize  i  gram 
of  fat.  This  is  called  the  acid  number.  When  sodium  hydroxid 
is  used  for  -titration,  the  acid  number  may  be  calculated  by 
multiplying  the  quantity  of  sodium  hydroxid  required  for  i  gram 
of  sample  by  1.4. 

Solubility  in  Acetic  Acid. — Valenta's  Test. — Fats  and 
oils  are  arranged  by  Valenta  into  three  classes,  according  to 
their  solubility  in  acetic  acid.  Equal  volumes  of  the  oil  and 
acid  are  placed  in  a  test-tube,  thoroughly  mixed,  and,  if  no 
solution  takes  place,  warmed. 

Class  I. — Completely  soluble  at  ordinary  temperature: 
Olive  kernel  oil ;  castor  oil. 

Class  2. — Completely  soluble  or  nearly  so  at  temperatures 
ranging  from  23°  up  to  the  boiling-point  of  glacial  acetic 
acid:  Palm  oil;  coconut  oil;  olive  oil;  cacao-butter;  sesame 
oil;  cottonseed  oil;  arachis  oil;  beef  tallow;  butter,  etc. 

Class  3. — Not  completely  dissolved  even  at  the  boiling- 
point  of  glacial  acetic  acid:  Oils  obtained  from  the  seeds  of 
the  Crucijerce;  rape-seed  oil;  mustard-seed  oil;  hedge-mustard 
oil. 

For  the  practical  appHcation  of  the  test  the  method  of  Chatta- 
way,  Pearmain,  &  Moor  is  satisfactory: 

2.75  grams  of  the  sample  are  weighed  in  a  short,  rather 
thick  tube  with  a  well-fitting  stopper,  3  c.c.  of  acetic  acid 


148  FOOD   ANALYSIS 

(99.5  per  cent.)  are  added,  the  tube  closed,  placed  in  a  beaker 
of  warm  water,  and  the  heat  increased  until,  after  well  shaking 
the  tube,  the  contents  become  quite  clear.  The  source  of  heat 
is  then  removed,  and  the  test-tube  so  placed  that  it  is  in  the 
center  of  the  beaker  of  heated  water,  and,  by  means  of  a  ther- 
mometer attached  to  the  tube  by  a  rubber  band,  the  whole 
is  allowed  to  rest  until  the  change  from  brilliancy  to  turbidity 
takes  place.  The  change  is  very  definite,  and  can  be  repeated 
as  often  as  is  wished,  with  a  maximum  error  of  about  0.25°. 

Thermal  Reaction  with  Sulfuric  Acid.— Maumene's 
Test. — Maumene^*  found  that  on  mixing  sulfuric  acid  with 
drying  oils  a  higher  temperature  is  produced  than  with  non- 
drying  oils.  With  the  same  sample  the  temperature  will 
depend  upon  the  acid.  The  strength  of  acid  employed  should 
be  determined  by  titration,  since  the  specific  gravity  of  the  acid 
of  96  per  cent,  and  of  99  per  cent,  is  practically  identical.  L. 
Archbutt  recommends  the  following  method  of  operating: 
50  grams  of  the  sample,  weighed  closely,  are  placed  in  a  beaker 
of  200  c.c.  capacity,  and,  together  with  the  bottle  of  acid,  placed 
in  water  until  both  have  acquired  its  temperature,  the  thermom- 
eter having  been  placed  in  the  oil.  The  beaker  is  removed, 
wiped,  and  placed  in  a  nest  of  cardboard  having  hollow 
sides  stuffed  with  cotton.  (A  beaker,  lined  with  cotton,  or, 
better,  a  vacuum  jacketed  test-tube,  may  also  be  used.)  The 
temperature  having  been  noted,  10  c.c.  of  acid  are  rapidly  with- 
drawn from  the  bottle,  which  is  immediately  closed,  the  acid  is 
allowed  to  flow  into  the  oil  while  it  is  being  stirred  with  the 
thermometer,  and  the  stirring  is  continued  until  no  further  rise 
of  temperature  is  observed.  The  stirring  must  be  so  managed 
as  to  effect  as  perfect  admixture  of  the  oil  and  acid  as  possible, 
thereby  insuring  an  even  development  of  heat  throiighout  the 
mixture. 

The  best  results  are  obtained  with  an  acid  about  97  per 
cent.     It  is  desirable  to  keep  on  hand  a  ^stock  of  oil  of  known 


FATS   AND   OILS  -  1 49 

purity,  and  to  test  some  of  this  with  each  set  of  samples 
examined. 

Specific  Temperature  Reaction. — The  discrepancies  ob- 
served in  Maumene's  method  may  be  largely  eliminated  by 
that  devised  by  Thomson  &  Ballentyne,"  which  is  to  compare 
the  rise  of  temperature  with  oil  and  with  an  equal  volume  of 
water  under  similar  conditions.  The  number  obtained  by 
dividing  the  oil  figure  by  the  water  figure  is  multiplied  by  loo 
to  eliminate  decimals,  and  the  datum  so  obtained  is  called  the 
specific  temperature  reaction. 

Bromin  Thermal  Value. — Hehner  &  Mitchell^®  ascertained 
that  the  heat  evolved  in  the  reaction  of  bromin  with  unsaturated 
fatty  bodies  furnishes  more  definite  data  than  does  sulfuric 
acid.  As  the  action  of  bromin  may  be  violent,  it  is  moderated 
by  a  diluent  such  as  chloroform,  carbon  tetrachlorid,  or  glacial 
acetic  acid.  The  latter  has  the  advantage,  owing  to  its  high 
boiling-point,  of  allowing  a  wider  range  of  temperature.  The 
procedure  is  as  follows:  The  bromin,  oil,  and  diluent  are  all 
brought  to  the  same  temperature,  i  gram  of  the  oil  is  dissolved 
in  10  c.c.  of  chloroform  in  a  vacuum- jacketed,  test-tube.  Ex- 
actly I  c.c.  of  bromin  (measured  by  means  of  a  pipet,  connected 
at  the  upper  end  with  a  narrow  tube  filled  with  caustic  lime,  and 
having  an  asbestos  plug  at  each  end)  is  added  and  the  rise  of 
temperature  determined  by  a  thermometer  graduated  into 
fifths.  Acids  are  dissolved  in  glacial  acetic  acid  instead  of 
chloroform. 

A  definite  relation  exists  between  the  iodin  number  and  the 
heat  produced  by  bromin.  In  Hehner  &  Mitchell's  experi- 
ments it  was  found  that  if  the  rise  of  temperature  in  degrees 
was  multiplied  by  5.5,  a  close  approximation  to  the  iodin 
number  was  always  obtained,  except  with  rape  and  linseed 
oils,  but  each  observer  must  ascertain  the  factor  applying  to 
particular  cases. 

Wiley"  has  made  this  method  more  accurate  and  more  easy 


150  FOOD  ANALYSIS 

of  application.  A  solution  of  bromin  in  four  parts  by  volume 
of  chloroform  or  carbon  tetrachlorid  is  employed.  This  is  to 
be  made  up  in  quantity  sufficient  for  one  day's  use,  and  kept 
in  the  dark.  Dissolving  the  sample  in  similar  solvents  is  an 
additional  convenience.  10  grams  of  the  sample,  in  sufficient 
chloroform  or  carbon  tetrachlorid  to  make  50  c.c.  of  solution, 
will  suffice  for  nine  determinations.  At  least  four  determina- 
tions should  be  made.  The  apparatus  is  shown  in  figure  41. 
The  tube  for  holding  the  reagent  and  thermometer  is  about 
40  cm.  in  length,  and  1.5  cm.  internal  diameter.  It  is  conveni- 
ently held  in  a  drying  jar,  being  fitted  air-tight  by  a  rubber 
stopper.  Air  is  withdrawn  from  the  jacketing  jar  through  the 
side  tubulure.  The  bromin  solution  is  contained  in  a  stout- 
walled  conical  flask  with  a  side  tubulure  provided  with  a  rubber 
bulb.  Through  the  stopper  passes  a  pipet,  and  the  flask  may 
be  rendered  air-tight  by  gentle  pressure  on  the  stopper.  The 
thermometer  should  be  graduated  to  0.2°  and  be  read  to  a  tenth 
by  a  lens.  The  operation  should  be  conducted  in  a  room  at 
uniform  temperature. 

The  solutions  and  apparatus  are  allowed  to  stand  until  all 
reach  a  uniform  temperature.  5  c.c.  of  the  solution  of  the 
sample  are  placed  in  the  inner  tube  by  means  of  the  pipet, 
without  allowing  any  of  the  solution  to  run  down  the  walls 
of  the  tube,  the  thermometer  is  inserted,  and  the  bromin  so- 
lution is  forced  up  into  the  pipet  by  compressing  the  rubber 
bulb  until  the  Hquid  has  passed  the  mark  on  the  stem.  The 
top  of  the  pipet  is  closed  by  the  finger,  the  stopper  of  the  flask 
loosened,  and  the  liquid  allowed  to  run  out  until  it  reaches 
the  mark,  when  it  is  transferred  to  the  mixing  tube  and  allowed 
to  flow  directly  into  the  solution  of  fat,  but  it  is  now  not  neces- 
sary to  prevent  the  liquid  running  down  the  side  of  "the  tube. 
The  empty  pipet  is  returned  to  the  flask  and  the  thermometer 
is  observed  at  once  by  means  of  a  lens,  since  the  bromination 
is  practically  instantaneous,  the  mercury  reaching  its  maximum 


FATS   AND   OILS 


151 


height  in  about  a  minute  after  the  pipet  is  withdrawn.  When 
the  mercury  begins  to  fall,  air  is  admitted  to  the  jacketing 
space,  the  mixing  tube  is  withdrawn,  its  contents  emptied,  and 


Fig.  41. 

the  tube  held  inverted  until  the  residual  bromin  vapor  escapes. 
The  tube  may  be  cleaned  by  wiping  it  with  a  long  test-tube 
cleaner  or  may  be  used  again  without  cleaning,  after  standing 


152 


FOOD   ANALYSIS 


inverted  for  half  an  hour.  Traces  of  brominated  oil  which 
may  remain  upon  the  side  of  the  tube  do  not  interfere  unless 
they  obscure  the  thermometer.  By  the  above  manipulation 
the  thermometer  soon  returns  to  the  room  temperature,  and  a 
second  determination  may  be  made  in  half  an  hour. 

As  noted  by  Hehner  &  Mitchell,  each  analytic  system  must 
be  separately  standardized  and  the  factor  for  calculating  the 
iodin  absorption  determined.  It  is  important  not  to  stir  or 
churn  the  mixture  of  oil  and  bromin  further  than  is  produced 
by  the  running  in  of  the  solution  itself.  Carbon  tetrachlorid  is 
the  preferable  solvent,  but  the  rise  of  temperature  is  slightly 
higher  with  chloroform. 

Gill  &  Hatch^^  have  proposed  to  facilitate  the  comparison  of 
tests  made  with  different  apparatus  by  employing  a  standard- 
izing material,  and  recommend  sublimed  camphor  for  this 
purpose.  7.5  grams  of  the  camphor  are  dissolved  in  carbon 
tetrachlorid,  the  solution  made  up  to  25  c.c,  and  portions  of 
5  c.c.  each  brominated.  The  temperature  increase  obtained 
with  various  oils  is  divided  by  the  rise  observed  with  camphor, 
giving  a  specific  temperature  increase,  analogous  to  that  sug- 
gested by  Thomson  &  Ballantyne  (see  p.  149).  By  dividing 
the  iodin  value  of  an  oil  by  the  specific  temperature  increase, 
a  figure  will  be  obtained  by  which  the  iodin  value  may  be  ap- 
proximately calculated. 

Elaidin  Test. — i  c.c.  of  mercury  is  dissolved  in  12  c.c.  of 
cold  nitric  acid  of  1.42  specific  gravity.  2  c.c.  of  the  freshly- 
made  deep  green  solution  are  shaken  in  a  wide-mouthed  stop- 
pered bottle  with  50  c.c.  of  the  sample  to  be  tested  and  the 
agitation  repeated  every  ten  minutes  during  two  hours.  When 
treated  in  this  manner,  oils  consisting  of  nearly  pure  olein  or 
of  mixtures  of  olein  with  solid  esters,  such  as  palmitin  and  stearin, 
give  more  or  less  solid  product.  OKve  oil  is  remarkable  for  the 
firmness  of  the  canary  or  lemon-yellow  mass  formed.  After 
24  hours  the  product  is  impervious  to  a  glass  rod,  and  some- 


FATS   AND   OILS  153 

times  rings  when  struck;  but  this  character  is  also  possessed 
by  the  elaidins  yielded  by  thfe  arachis  and  lard  oils.  In  making 
the  test,  it  is  important  to  note  the  time  required  to  obtain  a 
"solid"  product,  which  will  not  move  on  shaking  the  bottle, 
as  well  as  the  final  consistence.  The  temperature  should  be 
kept  nearly  constant,  or  erratic  effects  will  occur. 

The  behavior  of  the  more  important  oils,  when  tested  in  the 
foregoing  manner,  is  described  by  Allen  as  follows : 

A  hard  mass  is  yielded,  among  others,  by  olive,  almond, 
lard,  and  sometimes  arachis  oils. 

A  product  oj  the  consistency  oj  butter  is  given  by  mustard,  and 
sometimes  by  arachis  and  rape  oils. 

A  pasty  or  buttery  mass  which  separates  jrom  a  fluid  portion 
is  yielded  by  rape,  sesame,  cottonseed,  sunflower,  and  some- 
times mustard  oils.  Liquid  products  are  yielded  by  linseed, 
hempseed,  walnut  and  other  drying  oils. 

The  results  of  the  elaiden  test  must  be  accepted  with  caution, 
since  it  is  affected  by  many  conditions,  such  as  temperature, 
shape  of  the  containing  vessel,  and  the  mode  of  preparation 
of  the  acid  liquid.  The  extent  to  which  the  sample  has  been 
exposed  to  light  and  air  is  a  still  more  important  factor;  it  has 
been  shown  that  olive  oil  after  exposure  to  sunlight  for  two 
weeks  may  fail  to  respond  to  the  test. 

Index  of  Refraction. — This  datum  differs  notably  in  dif- 
ferent oils,  but  it  is  not  of  much  value  in  detecting  adulteration 
unless  considerable  of  the  adulterant  be  present.  Several  in- 
struments have  been  devised  for  making  refraction  determina- 
tion; the  familiar  ones  are  the  refractometer  of  Abbe  (figure  42) 
and  the  butyro-rcfractometcr  of  Zeiss  (figure  43). 

The  butyro-refractometer  has  been  strongly  recommended 
for  the  examination  of  butter.  It  is  equally  adapted  for  the 
general  examination  of  fats  and  oils,  and  may  be  used  for  the 
determination  of  the  index  of  refraction  as  well.  As  these 
instruments  are  made  by  only  one  firm  and  are  furnished  with 
directions  for  use,  further  description  will  not  be  required. 


154 


FOOD   ANALYSIS 


Drying  Property. — Livache's  Test.^® — The  so-called  drying 
of  oils  (a  process  of  oxidation)  is  hastened  by  admixture  with 
finely  divided  lead.  This  is  prepared  by  precipitating  lead 
acetate  by  zinc,  washing  the  precipitate  rapidly  with  water, 
alcohol,  and  ether  in  succession,  and  drying  at  very  low  pres- 
sure. (Probably  drying  in  nitrogen  gas  would  be  preferable.) 
I  gram  of  the  dried  lead  is  mixed  on  a  watch-glass  with  not 


Fig.  42. 


Liu.  43. 


more  than  0.7  gram  of  the  sample  by  dropping  the  latter  so 
that  it  is  distributed  over  the  mass,  of  the  lead.  The  glass  is 
allowed  to  stand  at  room  temperature  exposed  to  light,  but 
reasonably  protected  from  dust. 

Drying  oils  absorb  the  maximum  quantity  of  oxygen  after 
from  18  hours  to  3  days,  but  non-drying  oils  do  not  begin  to 
gain  weight  until  after  4  or  5  days.     Fat-acids,  except  those 


FATS   AND   OILS  155 

from  cottonseed  oil,  behave  the  same  as  the  fats.  Livache's 
results  are  given  in  the  following  table.  The  figures  show  the 
percentage  of  increase  in  weight  after  the  time  specified.  A 
drying  oil  (linseed)  is  added  for  comparison  with  the  food  oils. 
The  figure  for  maize  oil  is  given  by  Vult6  &  Gibson. 

Oil.  2  Days.  7  Days.  10  Days. 

Olive, o  1.7 

Cottonseed, 5.9 

Maize, 5.0 

Arachis, o  1.8 

Sesame, o  2.4 

Rape, o  2.9 

Linseed, 14.3 

Soluble  and  Insoluble  Acids. — This  method,  due  to  Hehner 
&  Angell,^"  has  been  much  modified  by  other  investigators.  The 
proportion  of  acids  insoluble  in  water  is  often  called  the  Hehner 
value.  The  following  method,  described  by  Allen,  is  some- 
what different  from  that  recommended  by  the  A.  O.  A.  C,  but 
will  serve  for  practical  purposes,  it  being  understood  that  blank 
tests  and  tests  with  standard  oils  should  be  made  for  comparison : 
About  5  grams  of  the  sample,  accurately  weighed,  are  placed 
in  a  saponification  flask,  50  c.c.  of  a  solution  of  40  grams  of 
sodium  hydroxid  to  looo  c.c.  of  alcohol  added,  the  flask  closed, 
and  the  mixture  heated  in  a  steam-bath  until  complete  saponi- 
fication has  occurred.  The  flask  is  cooled,  the  soap  solution 
acidulated  with  sulfuric  acid,  the  aqueous  Hquid  separated 
from  the  layer  of  fatty  acids,  and  the  latter  several  times  boiled 
with  a  considerable  quantity  of  water  in  a  flask  furnished  with  a 
reflux  condenser.  The  liquids  resulting  from  these  operations 
are  separated  from  the  insoluble  fatty  acids,  which  it  is  desirable 
to  boil  again  with  a  moderate  quantity  of  water,  while  driving 
a  current  of  steam  through  the  flask  in  which  they  are  con- 
tained, collecting  the  distillate,  and  treating  it  like  the  wash- 
ings.    The  acidulated  aqueous  liquid  first  separated  from  the 


156  FOOD   ANALYSIS 

layer  of  fatty  acids  is  then  distilled  to  a  small  bulk,  and  the  dis- 
tillate exactly  neutralized  with  standard  sodium  hydroxid,  using 
phenolphthalein  as  an  indicator.  The  first  washings  from  the 
insoluble  fatty  acids  are  then  added  to  the  contents  of  the  dis- 
tilling flask,  and  the  liquid  again  distilled  to  a  small  bulk,  the 
process  being  repeated  with  the  succeeding  washings.  The 
different  distillates  should  be  titrated  separately  with  decinor- 
mal  alkali  and  phenolphthalein,  so  that  the  progress  and  com- 
pletion of  the  washing  may  be  followed,  and  some  information 
obtained  as  to  the  nature  and  relative  proportions  of  the  lower 
jatty  acids  present. 

The  neutralized  distillates  should  be  united  and  evaporated 
gently  to  dryness,  and  the  residue  dried  at  100°  until  the  weight 
is  constant.  It  consists  of  the  sodium  salts  of  the  acids  that 
passed  over  in  the  distillation.  If  the  number  of  cubic  cen- 
timeters of  -^  sodium  hydroxid  employed  for  neutralization 
be  multiplied  by  0.22,  and  the  product  be  subtracted  from  the 
weight  of  the  dry  residue,  the  difference  will  be  weight  of  the 
volatile  acids. 

When  coconut  oil  and  palmnut  oil  are  treated  in  this  man- 
ner, the  distillate  will  be  found  to  contain  lauric  acid,  which, 
though  almost  insoluble  in  water,  is  volatile  in  a  current  of 
steam.  It  may  be  separated  from  the  more  soluble  volatile 
fatty  acids  by  filtering  the  distillate. 

Acetyl  Value. — This  determination,  originally  suggested 
by  Benedikt,  is  most  conveniently  carried  out  by  the  method 
of  Lewkowitsch^^:  10  grams  of  the  sample  are  boiled  for  two 
hours  with  an  equal  volume  of  acetic  anhydrid  in  a  flask  pro- 
vided with  an  inverted  condenser;  the  mass  is  then  transferred 
to  a  larger  beaker,  diluted  with  several  hundred  cubic  centi- 
meters of  water,  and  boiled  for  30  minutes,  with  a  slow  current 
of  carbon  dioxid  passed  through  by  means  of  a  tube  drawn  out 
to  a  fine  opening  at  the  lower  end.  This  prevents  bumping. 
On  cooling,  two  layers  are  formed.     The  water-layer  is  drawn 


FATS   AND   OILS  1 57 

off  by  a  siphon  and  the  other  portion  washed  three  times  by 
boiling  with  convenient  measures  of  water.  Prolonged  wash- 
ing should  be  avoided.  The  acetylated  product  is  freed  from 
water  by  filtration  through  a  dry  filter  in  a  water-oven  at  ioo°. 

5  grams  of  the  substance  are  saponified  as  noted  on  page 
145,  the  alcohol  is  evaporated,  and  the  soap  dissolved  in  water. 
The  subsequent  operations  may  now  be  completed  by  two 
methods,  "distillation"  or  "fikration."  The  latter  is  the 
shorter  and  more  convenient. 

Distillation  Method. — The  liquid  is  made  up  to  a  volume  of 
several  hundred  cubic  centimeters  in  a  flask  fitted  with  an 
arrangement  for  passing  in  steam  or  for  adding  water  from 
time  to  time.  Sufficient  dilute  sulfuric  acid  (i  part  of  acid  to 
10  of  water)  is  added  to  make  the  liquid  slightly  acid,  and  dis- 
tillation is  carried  on  until  about  700  c.c.  are  collected.  The 
distillate  is  filtered  and  titrated  with  decinormal  alkali.  Phe- 
nolphthalein  is  recommended  as  an  indicator,  but  probably 
methyl- orange  will  serve  as  well.  The  number  of  cubic  cen- 
timeters of  solution  required  to  neutralize  the  distillate,  mul- 
tiplied by  5.61  and  the  product  divided  by  the  weight  of  the 
acetylated  material,  gives  the  acetyl  number. 

Filtration  Method. — The  solution  of  the  saponified  acetyl- 
ated substance  is  mixed  with  sufficient  standard  sulfuric  acid 
to  be  equivalent  to  the  alkali  added  for  saponification,  and  the 
mixture  warmed  gently.  The  acids  will  separate  as  an  oily 
layer.  The  layer  is  removed,  washed  with  boiling  water  until 
the  washings  are  not  acid,  titrated  with  decinormal  alkali,  and 
the  acetyl  number  calculated  as-above. 

The  acetyl  number  is  the  number  of  milligrams  of  potas- 
sium hydroxid  required  for  neutrahzin^  the  acetic  acid  ob- 
tained from  I  gram  of  the  acetylated  substance. 

In  this  process  cholesterol  and  phytosterol  are  included  in 
the  acetyhzation. 

Substances  yielding  volatile  acids  give  an  acetyl  number 


158 


FOOD  ANALYSIS 


too  high ;  this  condition  will  affect  the  distillation  method  more 
than  the  filtration  method.  To  ehminate  most  of  this  error, 
the  percentage  of  volatile  acid  should  be  determined  and  the 
figures  obtained  deducted  from  the  acetyl  number. 

The  water  used  in  both  methods  should  be  freed  as  far  as 
possible  from  carbon  dioxid.  Even  the  water  used  in  pro- 
ducing the  open  steam  should  be  brought  to  active  boihng  be- 
fore the  steam  is  let  into  the  flask.  Waters  rich  in  carbonate 
are  especially  objectionable.     A  slight  excess  of  sulfuric  acid 

causes  the  insoluble  acids  to  separate 
better,  but  this  must,  of  course,  be 
known  accurately  and  allowance  made 
for  it. 

It  is  possible  that  the  data  elucidated 
by  Richmond  with  regard  to  the  rate 
of  distillation  of  acids  of  the  acetic 
series  could  be  applied  to  the  distilla- 
tion method  with  advantage,  but  a 
special  investigation  will  be  needed  to 
determine  the  point. 

Viscosity . — Practical  determina- 
tions of  viscosity  are  comparative  only 
and  are  of  little  value  unless  uniform 
methods  are  employed.  Many  forms 
of  viscosimeter  have  been  devised. 
They  are  of  two  types,  resistance  and 
flow  instruments.  In  the  former,  the  viscosity  is  measured  by 
the  resistance  to  the  movement  of  an  immersed  solid;  in  the 
latter,  the  time  required  for  the  flow  of  a  given  volume  of 
liquid  is  measured.  Doolittle's  torsion  viscosimeter  is  the  best 
of  its  class;  Reilly's  (figure  44)  is  the  best  of  the  second  class. 
Descriptions  of  these  instruments  and  of  methods  of  operation 
are  unnecessary,  as  they  are  made  according  to  standard 
patterns  and  full  working  directions  are  furnished  with  them. 


Fig.  44. 


FATS   AND   OILS  1 59 

Blasdale^^  investigated  the  relative  viscosities  of  solutions  of 
soap  from  different  grades  of  olive  oils  and  found  the  figures 
of  much  value.  He  used  the  torsion  viscosimeter.  The  prepa- 
ration of  the  solution  is  as  follows:  15  grams  of  the  sample 
are  saponified  with  a  mixture  of  10  c.c.  of  alcohol  and  30  c.c. 
of  water  containing  7.5  grams  of  potassium  hydroxid.  The 
mass  is  washed  into  a  large  dish,  heated  until  the  alcohol  is  re- 
moved, diluted  to  500  c.c.  at  20°,  and  the  viscosity  determined. 
The  result  is  expressed  by  Blasdale  in  the  number  of  grams  of 
sugar  that  it  would  be  necessary  to  add  to  a  liter  of  water  to  get 
the  same  readings.  With  some  oils  it  would  be  necessary  to 
dilute  the  solution  to  1000  c.c. 

Blasdale's  results  were  as  follows: 

Oils.  Viscosity. 

Olive  (California), 573-655 

Cottonseed, 280 

Arachis, 220 

Sesame, 415 

Rape, 670 

Sweet  almond, 645 

Mustard-seed  oils  give  high  viscosity  figures,  and  a  mixture 
of  these  with  cottonseed  oil  in  some  proportions  would  escape 
detection  by  this  test. 

Unsaponifiable  Matter. — Most  fats  and  oils  contain  un- 
saponifiable  matters,  the  extraction  and  examination  of  which 
are  useful  data.  The  operation  is  most  conveniently  performed 
by  saponifying  with  a  solution  of  sodium  (or  potassium)  hy- 
droxid in  alcohol,  evaporating  the  alcohol,  dissolving  in  water, 
and  extracting  this  solution  with  ether.  The  extraction  of 
the  dry  soap  with  ether  is  not  so  satisfactory.  The  use  of  the 
watery  solution  is  due  to  Allen.  The  operation  is  most  con- 
veniently carried  out  in  a  stoppered  separator. 

Separation  does  not  always  occur  readily,  but  may  often  be 
induced  by  cooling  the  contents  by  adding  a  little  sodium  hy- 


l6o  FOOD   ANALYSIS 

droxid  solution,  more  ether,  or  a  few  cubic  centimeters  of  alcohol 
and  rotating  the  mass  gently.  The  aqueous  liquid  is  run  out,  a 
few  drops  of  sodium  hydroxid  solution  and  lo  ex.  of  water  are 
added,  gently  agitated,  and  run  off.  This  treatment  is  repeated, 
after  which  the  ether  is  run  off  in  a  tared  flask,  the  aqueous 
liquid  is  agitated  with  a  fresh  portion  of  ether,  which  is  washed 
and  poured  into  the  tared  vessel  as  before.  This  process  is 
again  performed,  when  it  will  be  complete.  The  ethereal  solu- 
tion may  be  fluorescent  if  petroleum  products  are  present. 
The  greater  portion  of  the  ether  should  be  distilled  off  in  a 
recovering  apparatus  and  the  rest  evaporated  in  the  water  bath. 
If  the  mass  retains  globules  of  water,  the  flask  should  be  held 
horizontally  and  rotated  rapidly  so  as  to  spread  the  residue  in 
a  thin  layer.  When  no  more  water  is  visible  and  the  odor  of 
ether  is  very  slight,  the  flask  is  placed  on  its  side  in  the  water- 
oven  for  15  minutes,  cooled,  and  weighed. 

Long  heating  should  be  avoided,  as  some  hydrocarbons  are 
sensibly  volatile  at  100°.  Spermaceti  and  waxes  yield  in  this 
process  a  large  percentage  of  unsaponifiable  matter,  hence  it 
is  not  available  for  the  detection  of  paraffin  in  such  substances. 

In  ordinary  cases  the  distribution  of  the  bodies  will  be  as  fol- 
lows, but  some  resins  will  pass  into  the  water  in  the  form  of 
sodium  salts : 

In  the  Ether:  In  the  Water: 

Hydrocarbons.  Sodium  salts. 

Mineral  oils.  Glycerol. 

ParaflSn.  Sodium  hydroxid. 

Neutral  resins. 

Coloring-matters  from  palm  oil. 
Cholesterol  and  analogs. 

Cholesterol  and  Analogs. — In  the  examination  of  commer- 
cial edible  oils,  the  cholesterols  are  the  most  important  of  the 
above  ingredients.  Cholesterol  is  a  member  of  a  series  of  alco- 
hols, having  physical  characters  somewhat  like  those  of  fats. 
There  are  a  number  of  homologs,  but  the  individual  members 


FATS   AND   OILS  l6l 

of  the  group  with  a  few  exceptions  have  been  but  little  studied. 
Cholesterol  occurs  abundantly  in  some  animal  fats,  such  as 
wool-grease,  and  has  been  supposed  to  be  present  in  olive  oil  as 
an  exception  among  vegetable  oils,  but  the  investigations  of  Gill 
&  Tufts  ^^  have  made  this  doubtful.  Vegetable  oils  contain  anal- 
ogous bodies.  Among  the  most  common  of  these  is  phytosterol. 
Some  cereals  contain  a  homolog  termed  sitosterol^  and  oils  from 
these  seeds  will  be  liable  to  contain  it. 

A  general  method  for  the  extraction  of  these  substances  is 
that  of  Foster  &  Riechelmann:  50  grams  of  the  fat  are  twice 
boiled,  for  about  30  minutes  at  a  time,  with  75  c.c.  of  alcohol  in 
a  flask  fitted  with  an  inverted  condenser,  the  flask  being  mean- 
while well  shaken.  The  alcoholic  solution  is  mixed  with  15 
c.c.  of  30  per  cent,  sodium  hydroxid  solution,  and  boiled  on 
the  water-bath  in  a  flask  fitted  with  a  condensation  tube  until 
about  one-fourth  of  the  alcohol  is  evaporated.  The  fluid  is 
then  evaporated  nearly  to  dryness  in  a  porcelain  basin  and  the 
residue  shaken  with  ether.  The  ethereal  solution  is  evaporated 
to  dryness,  the  residue  dissolved  in  about  40  c.c.  of  water, 
shaken  out  with  a  mixture  of  75  c.c.  of  ether  and  3  c.c.  of  alcohol, 
the  solvent  removed,  washed  three  times  with  water,  evaporated, 
and  the  residue  crystallized  from  alcohol. 

Von  Raumer  determines  the  amount  of  crude  cholesterol  as 
follows:  50  grams  of  the  oil  are  saponified  with  alcoholic  po- 
tassium hydroxid.  The  resulting  soap  is  evaporated  to  dryness, 
reduced  to  powder,  and  extracted  with  50  to  75  c.c.  of  ether  in 
a  Soxhlet  apparatus,  plugs  of  fat-free  cotton  being  placed  above 
and  below  the  layer  of  soap.  The  residue  is  saponified  again 
with  10  c.c.  of  half  normal  alkali  evaporated  to  dryness  with 
sand,  and  re-extracted  as  before  during  two  hours.  When 
the  work  is  carefully  5one,  the  second  Saponification  and  ex- 
traction is  unnecessary. 

The  following  amounts  of  residue  calculated  to  100  grams 
of  sample  were  obtained  by  this  method:  Cottonseed  oil,  0.719 
15 


l62 


FOOD  ANALYSIS 


gram;  sesame  oil,    1.3 14  grams  to   1.325   grams;  lard,  0.217 
gram. 

These  substances  are  insoluble  in  water,  sparingly  soluble 
in  cold  alcohol,  freely  in  boiling  alcohol,  and  in  the  other  com- 
mon solvents  immiscible  with  water  such  as  ether,  chloroform, 
petroleum  spirit.  They  are  distinguished  from  each  other  by 
melting-point,  crystalline  form  and  some  color  reactions  as  fol- 
lows : 


Cholesterol. 

Phytosterol. 

Sitosterol. 

Melting-point. 

145° 

132-4° 

137-8° 

Crystals  from  hot 

Rhombic    plates, 

Needles, 

Narrow     plates. 

alcoholic    solu- 

often  with   re- 

grouped      i  n 

with     pointed 

tion. 

entering  angles. 

tufts. 

terminals. 

Solution-    in 

Bluish    green 

Clear      green 

dilute        acetic 

becoming 

changing       to 

anhydrid    with 

reddish  yellow. 

pure  yellow. 

sulfuric  acid. 

Solution     in 

Blood  red. 

Blood      red 

Blood      red 

chloroform 

becoming 

becoming 

with    sulphuric 

cherry  red. 

purple. 

acid. 

The  color  reactions  are  obtained  by  dissolving  a  little  of  the 
sample  in  a  few  c.c.  of  the  solvent,  adding  strong  sulfuric  acid, 
shaking,  and  allowing  the  liquid  to  stand  for  some  time.  The 
results  are  somewhat  vague  and  it  is  not  impossible  that  a  por- 
tion of  the  action  is  due  to  unknown  impurities.  According  to 
Salkowski,  cholesterol  gives  with  chloroform  and  sulfuric  acid 
the  following  effects:  The  solution  immediately  becomes 
blood  red,  afterward  cherry  red  and  purple;  the  last  tint  re- 
mains for  several  days.  The  sulfuric  acid  layer  under  the 
chloroform  shows  a  strong  green  fluorescence.  On  pouring  a 
few  drops  of  the  purple  chloroform  layer  into  a  porcelain  basin, 
the  red  color  changes  rapidly  to  blue,  green,  and  finally  to  yellow. 
On  diluting  the  purple  chloroform  solution  with  more  chloro- 
form, it  becomes  nearly  colorless,  or  acquires  an  intense  blue; 


FATS   AND   OILS  1 63 

if  it  now  be  shaken  again  with  the  sulfuric  acid  layer,  the  former 
coloration  appears.  These  latter  changes  of  color  are  due  to 
traces  of  water  in  the  chloroform. 

The  solution  of  phytosterol  gives  the  same  reaction  with 
sulfuric  acid,  but  there  is  the  slight  difference  that  the  coloration 
obtained  with  the  former  passes  after  a  few  days  into  a  bluish- 
red,  whereas  the  cholesterol  solution  remains  more  of  a  cherry 
red.  In  the  crystallization  from  alcohol,  if  a  mixture  of  chole- 
sterol and  phytosterol  is  present,  the  crystals  show  one  form 
either  approximating  to  that  of  phytosterol  or,  if  cholesterol  is 
present  in  the  greater  quantity,  differing  from  the  pure  crystals 
of  either  body. 

Analytic  Data. — The  data,  commonly  termed  "con- 
stants," obtained  by  the  processes  described  in  the  preceding 
pages,  are  subject  to  uncertainty,  owing  to  the  want  of  abso-' 
lute  standards.  Fats  and  oils,  being  mixtures  of  several  in- 
gredients, will  vary  with  conditions  of  growth  of  the  animals 
or  plants  yielding  them,  methods  of  extracting  and  refining, 
exposure  to  light,  heat,  and  air,  and,  doubtless,  from  unrecog- 
nized causes.  Samples  prepared  in  the  laboratory  do  not 
necessarily  serve  as  standards  for  commercial  products.  Er- 
rors of  observation  from  defective  apparatus,  especially  in- 
accurate thermometers,  are  by  no  means  uncommon. 

The  data  for  specific  gravity  and  for  melting  and  solidifying 
points  given  in  the  following  tables  have  been  compiled  from 
the  best  accessible  sources,  and  will  give  a  general  idea  of  the 
range  of  figures  in  commercial  samples : 


164  FOOD   ANALYSIS 

SPECIFIC  GRAVITIES  OF  FATS,  OILS  AND  FATTY  ACIDS. 

Oils.  Acids. 

(iS.S°.)  (100°.)  (ioo°.) 

Olive, 0.914-0.918  0.875 

Cottonseed, 0.922-0.925  0.8725  0.882 

Maize, 0.922-925  0.871 1 

Coconut, 0.912  0.868-0.874  0.844 

Arachis, 0.916-0.922  0.847 

Sesame, 0.922-0.924 

Rape, 0.913-0.917  0.875-0.879 

Cacao-butter, S 0.948-0.976  0-857 

Lard, 0.932-0.938  0.859-0.864  0.837-0.840 

Tallow, 0.893-0.898  0.870 

Butter-fat, 0.926-0.940  0.909-0.914 

Coconut  olein, 0.926  0.907 

lODIN  NUMBERS  OF  FATTY  ACIDS. 
Oil  or  Fat.  Mixed  Acids.  Liquid  Acids. 

Olive, 86-90 

Cottonseed, 111-116  147 

Maize, 1 13-125  140 

Arachis, 95-103  1 28 

Sesame, 109-1 1 2 

Rape, 99-105 

Coconut, 8.5-9  54 

Cacao-butter, 32.5-39 

Butter-fat, 28-31 

Lard, 64-81  104 


MELTING  AND  SOLIDIFYING  POINTS  AND  TITER- 
The  titer-tests  were  determined  by  Lewkowitsch. 

Oil  or  Fat.  Acids 

Melting.  Solidifying.  Melting-point. 

Olive, 4  to — 2  24  to  27 

Cottonseed, i  to  10  35  to  40 

Maize, not  above  — 10  18  to  20 

Coconut, 20  to  28  14  to  23  24  to  2 7 

Arachis, — 5  28  to  ^^ 

Sesame, — 4  to  — 6  23  to  3 1 

Rape, — 6  to — 10  18  to  22 

Cacao-butter, 30  to  34  20  to  27  481052 

Lard, 281045  271044  351047 

Butler-fat, 29  to  35  20  to  30         36  to  46  (insol.) 

Beef  tallow, 36  to  49  33  to  48  43  to  47 

Mutton  tallow, 36  to  49  33  to  48  46  to  54 


TESTS. 


Titer-test. 
16.9  to  26.4 
32.2  1037.6 

21.2  to  25.2 

28.1  to  29.2 

21.2  to  23.8 

II. 7  to  13.6 

48.0  to  48.2 
41.4  to  42.0 

37.9  to  46.2 

40.1  to  48.3 


1 66  FOOD   ANALYSIS 

Special  Tests. — Several  tests  are  of  value  for  recognizing 
particular  oils  or  fats.  The  indications  for  their  use  will  be 
given  in  connection  with  these. 

Carbon  disulfid-suljur  test. — Halphen's  test. — This  is  in- 
tended for  the  recognition  of  cottonseed  oil.  It  is  applicable 
both  to  oils  and  mixed  acids. 

Carbon  disulfid  containing  about  i  per  cent,  of  sulfur  in 
solution  is  mixed  with  an  equal  volume  of  fusel  oil.  Equal 
volumes  of  this  reagent  and  the  sample  (about  3  c.c.  of  each) 
are  mixed  and  heated  in  a  bath  of  boiling  brine  for  15  min- 
utes. If  no  red  or  orange  tint  is  produced,  i  c.c.  of  the  re- 
agent is  added,  and  if  after  5  or  10  minutes  more  heating  no 
color  is  shown,  a  third  addition  of  i  c.c.  may  be  made.  It  is 
possible  to  detect  very  small  quantities  of  cottonseed  oil  by 
this  test.  Lard  and  lard  oil  derived  from  animals  fed  on  cot- 
tonseed meal  will  often  give  a  faint  reaction. 

Silver  nitrate  test. — Bechi^s  test. — This  is  a  test  for  cotton- 
seed oil.  Several  modifications  are  in  use.  According  to  Del 
Torre,  the  following  reagents  are  required : 

A 

Silver  nitrate, i  .0  gram. 

Alcohol, 200.0  c.c. 

Ether, 40.0  c.c. 

Nitric  acid, " o.i  gram. 

B 

Fusel  oil, loo.o  c.c. 

Rapeseed  oil, 15.0  c.c. 

10  C.C.  of  the  oil  to  be  examined  are  mixed  in  a  test-tube 
with  I  c.c.  of  reagent  A,  and  then  shaken  with  10  c.c.  of 
reagent  B.  The  mixture  is  next  divided  into  two  equal  por- 
tions, one  of  which  is  immersed  in  boiling  water  for  15 
minutes.  The  heated  sample  is  then  removed  from  the  water- 
bath,  and  its  color  compared  with  the  unheated  half.  Cotton- 
seed oil  is  indicated  by  the  reddish-brown  of  the  heated  portion. 


FATS  AND  OILS  167 

Only  the  purest  alcohol  should  be  used,  and  the  rapeseed  oil 
used  should  be  "cold  drawn,"  and  only  slightly  colored;  it 
should  be  filtered  in  a  hot-water  oven  before  preparing  the  re- 
agent. To  guard  against  errors  from  impurity  of  the  reagents, 
a  blank  test  should  be  made. 

It  is  stated  that  old  and  rancid  samples  will  not  react  unless 
the  rape  oil  be  present.  Most  chemists,  however,  do  not  use 
it,  especially  in  testing  lard.  Hehner  uses  reagent  A,  add- 
ing I  volume  to  2  volumes  of  oil  and  heating  for  15  minutes. 
Milliau  uses  A  with  the  mixed  fatty  acids;  but  experience  has 
shown  that  in  some  cases,  in  which  cottonseed  oil  was  present 
and  responded  to  the  test,  the  fatty  acids  failed  to  give  a  similar 
reaction.  After  heating  to  240°  or  on  long  keeping,  both  oil 
and  fatty  acids  may  fail  to  respond  to  the  test. 

Furjural  test. — Badouin^s  test. — This  is  a  test  for  sesame 
oil.  In  its  original  form,  the  sample  was  shaken  with  a  mix- 
ture of  sucrose  and  strong  hydrochloric  acid,  when  a  crimson 
is  produced  if  sesame  oil  be  present.  As  furfural  is  a  prod- 
uct of  the  action  of  hydrochloric  acid  on  sucrose,  and  is  the 
active  agent  in  the  test,  Villavecchia  &  Fabris  have  substi- 
tuted an  alcoholic  solution  of  the  latter  for  the  sugar.  The 
solution  is  made  dilute  (2  per  cent.),  as  furfural  itself  gives  a 
violet  tint  with  hydrochloric  acid.  The  modified  test  is  ap- 
plied in  one  of  the  following  forms : 

(a)  0.1  c.c.  of  the  2  per  cent,  furfural  solution  is  placed  in 
a  test-tube^  lo  c.c.  of  the  sample  and  10  c.c.  of  hydrochloric 
acid  (sp.  gr.  1.19)  added,  the  mixture  shaken  for  half  a  min- 
ute, and  allowed  to  settle.  In  the  presence  of  even  less  than 
I  per  cent,  of  sesame  oil,  the  aqueous  layer  will  become  crimson. 
In  the  absence  of  sesame  oil  the  lower  layer  is  either  colorless 
or,  at  most,  becomes,  as  in  the  case  of  very  rancid  though  pure 
olive  oil,  dirty  yellow. 

{h)  0.1  c.c.  of  the  furfural  solution  is  mixed  with  10  c.c.  of 
the  sample  and  i  c.c.  only  of  hydrochloric  acid  added;    the 


1 68  FOOD   ANALYSIS 

mass  shaken  thoroughly  and  separation  brought  about  by 
addition  of  lo  c.c.  of  chloroform,  or  by  a  centrifuge,  when 
the  aqueous  layer  will  be  crimson  with  even  less  than  i  per 
cent,  of  sesame  oil. 

Pyrogallol  test  (Tocher^ s  test). — i  gram  of  pyrogallol  is  dis- 
solved in  15  c.c.  of  hydrochloric  acid  and  shaken  with  an 
equal  volume  of  the  sample.  After  separation,  the  watery 
liquid  is  boiled.  Sesame  oil  produces  a  solution  that  is  red  by 
transmitted,  and  blue  by  reflected,  light. 

Brulle's  test,  o.i  gram  of  finely  powdered  egg  albumin  and  2 
c.c.  of  dilute  nitric  acid  (3  c.c.  of  nitric  acid  and  i  c.c.  of 
water)  are  mixed  with  10  c.c.  of  the  sample,  the  mixture  heated 
in  a  test-tube,  without  stirring,  to  boiling,  and  then  shaken 
cautiously  until  the  albumin  dissolves.  Care  must  be  taken 
in  this  as  the  action  may  be  violent.  Cottonseed,  arachis, 
rape  and  sunflower  oils  give  red  solutions;  olive  oil  and  lard 
yield  an  elaidin  but  no  color. 

OLIVE  OIL 

Olive  oil  is  obtained  from  the  fruit  of  the  Olea  europcea  L. 
Its  color  usually  ranges  from  light  yellow  to  golden  yellow,  but 
some  forms  are  deep  green  from  presence  of  chlorophyl.  The 
quality  of  the  oil  depends  on  many  conditions;  that  intended 
for  food  is  always  expressed  cold. 

Olive  oil  contains  about  28  per  cent,  of  solid  fat,  consisting 
of  palmitin  and  a  little  arachidin.  The  remainder  is  mostly 
olein,  with  a  little  linolin.  Hehner  &  Mitchell  found  no  stearin. 
Appreciable  amounts  of  cholesterol  are  present,  differing  from 
most  vegetable  oils,  which  contain  phytosterol.  The  un- 
saponifiable  matter  ranges  from  i  to  1.5  per  cent.  Free  fatty 
acid  is  always  present,  amounting  in  the  best  grades  to  about 
1.5  per  cent.,  and  in  the  lowest  grades  to  25  per  cent. 

Adulteration. — Olive  oil  is  very  liable  to  adulteration.  In 
this  country,  cottonseed  oil  and  arachis  oil  are  the  additions 


OLIVE    OIL  169 

most  commonly  employed.  In  many  cases  the  article  con- 
tains no  olive  oil,  cottonseed  oil  or  a  mixture  of  cottonseed 
and  arachis  oil  being  substituted.  Other  adulterants  are 
sesame,  rape,  poppyseed,  and  lard  oil.  Still  more  rarely, 
curcas  oil,  and  even  castor  oil  have  been  employed.  It  is 
stated  that  15  or  20  per  cent,  of  the  latter  may  be  present  with- 
out affecting  the  taste.  In  the  lower  grades  of  oil,  not  intended 
for  table  use,  any  ordinary  oil,  including  refined  petroleum, 
may  be  present. 

Specific  Gravity. — The  specific  gravity  of  olive  oil  usually 
ranges  from  0.914  to  0.917,  or  even  0.918  in  the  case  of  Cali- 
fornia oils.  Commercial,  usually  brown,  oils,  expressed  at 
a  high  temperature,  and  containing  a  higher  proportion  of 
•palmitin,  may  range  as  high  as  0.925.  A  specific  gravity  of 
0.918  or  over,  in  a  sample  of  light  color,  w^ould  give  rise  to 
suspicion  of  adulteration  with  cottonseed,  poppyseed,  or  se- 
same oil. 

Solidifying- point. — Olive  oil  has  usually  a  higher  solidifying- 
point  than  any  other  of  the  vegetable  oils.  Mixtures  of  olive 
with  other  oils  have,  as  a  rule,  a  lower  melting-point  than  either 
constituent  alone.  The  melting  and  solidifying  points  of  the 
mixed  acids  are  also  of  some  value,  but,  according  to  Dieterich, 
less  than  25  per  cent,  of  adulteration  cannot  be  detected  with 
certainty. 

Saponification  Value. — This  determination  is  of  use  only  in 
the  case  of  adulteration  with  a  considerable  proportion  of  rape 
oil. 

lodin  Number. — This  determination  furnishes  the  most 
valuable  indications  of  the  purity  of  olive  oil.  The  figure  for 
pure  oil  usually  ranges  between  81.5  and  85  per  cent.  Values 
as  high  as  88.6  have  been  reported  from  some  California  oils, 
but  such  samples  are  exceptional,  and  a  figure  above  85  should 
give  rise  to  suspicion  of  adulteration. 

Heat  of  Bromination. — Specific  Temperature  Reaction. — The 
16 


lyo  FOOD   ANALYSIS 

thermal  values  of  olive  oil  are  lower  than  those  of  other  vege- 
table oils  and  the  determination  is  frequently  of  use. 

Elaidin  Test. — Olive  oil  yields  the  hardest  elaidin  of  all  the 
oils,  and  in  the  shortest  time,  but,  as  noted  on  page  153,  too 
much  reliance  must  not  be  placed  upon  the  indications  of 
this  test.  The  following  figures,  obtained  by  Blasdale  from 
fresh  Cahfornia  oils,  of  known  purity,  serve  to  show  that  the 
times  required  to  form  a  solid  product  may  differ  much : 

Time  Required  for 
Brand  of  Oil.  Elaidin  Test. 

Uvaria, 6  hours. 

Pendulina, 4      " 

Redding  Pecholine, 3      " 

Nevadillo  bianco, 2      " 

Manzanillo, 30  minutes. 

Refractive  Power. — The  refractive  power  of  olive  oil  is  less 
than  that  of  any  other  of  the  vegetable  oils.  The  determination 
of  the  refractive  index  gives  reliable  indications  only  in  the 
presence  of  a  considerable  proportion  of  the  adulterant.  The 
most  satisfactory  results  are  obtained  by  the  butyrorefracto- 
meter.     (See  table  on  page  165.) 

Nitric  acid  test. — This  will  detect  small  amounts  of  cotton- 
seed oil  in  olive  oil.  Some  operators  employ  acid  of  1.41  spe- 
cific gravity,  but,  according  to  Lewkowitsch,^*  one  of  1.375  gives 
better  results.  He  recommends  that  the  mixture  be  allowed  to 
stand  about  24  hours,  when  olive  oil  containing  cottonseed  oil 
becomes  pure  brown;  but  if  rape  oil  be  present,  the  mixture 
becomes  more  yellowish.  Attention  has  been  called  to  the  fact 
that  some  highly  purified  cottonseed  oils  react  so  faintly  with 
nitric  acid  that  samples  containing  as  much  as  10  per  cent, 
showed  no  reaction. 

The  following  is  a  summary  of  tests  adapted  to  detection  of 
the  particular  adulterations  noted : 

Cottonseed  Oil.     Halphen's  test;    nitric  acid  color  test; 


COTTONSEED  OIL  171 

Bechi's  test;  iodin  number;  Livache's  test;  temperature  re- 
actions; viscosity  of  soap  solution.     Brulle's  test. 

Arachis  Oil.  Viscosity  of  soap  solution;  determination 
of  arachidic  acid;  iodin  number.     Brulle's  test. 

Rape  Oil.  Iodin  number;  Palas'  test;  melting  and  solid- 
ifying points  of  acids ;  acetic  acid  test ;  refractive  index. 

Sesame  Oil.  Furfural  tests;  pyrogallol  test;  iodin  absorp- 
tion; temperature  reactions;  saponification  value. 

Some  true  olive  oils  give  a  reaction  simulating  sesame  oil  with 
the  furfural  test,  but  this  confusion  may  be  avoided  by  using 
the  mixed  fatty  acids;  the  olive  oil  acids  do  not  give  the  reaction. 

Lard  Oil.  Melting-point  of  fatty  acids;  odor  of  lard  on 
warming. 

Seed  Oils  collectively.     Separation  of  cholesterol  analogs. 

Castor  Oil.  Solubility  in  acetic  acid  in  the  cold;  solubil- 
ity in  absolute  alcohol ;  specific  gravity. 

CuRCAS  Oil.  Iodin  value;  saponification  value.  Treated 
with  nitric  acid  and  copper,  an  intense  reddish-brown  is  pro- 
duced in  presence  of  as  little  as  10  per  cent,  of  curcas  oil. 

Hydrocarbon  Oils.  Determination  of  unsaponifiable  mat- 
ter. 

Green  olive  oil  has  been  imitated  by  coloring  other  oils  with 
copper  acetate.  All  green  oils  should  be  tested  for  copper  by 
boiling  with  hydrochloric  acid  and  testing  the  acid  solution, 
as  described  on  p.  58. 

COTTONSEED  OIL 

Cottonseed  oil  is  obtained  from  seeds  of  several  species  of 
Gossypium.  The  crude  product  is  dark  red.  It  is  refined  by 
treatment  with  alkali.  The  refined  oil  is  pale  yellow,  of  pleas- 
ant flavor,  and  neutral,  but  becomes  rancid  gradually,  when  free 
acid  is  also  formed  and  a  so-called  ''stearin"  deposited.  The 
better  grades  of  oil  are  sold  after  being  freed  from  stearin  by 
chilling  or  long  standing.     The  refined  oil  is  used  for  cooking 


172  FOOD   ANALYSIS 

purposes  and  as  a  salad  oil,  as  an  adulterant  for  olive  oil,  butter, 
lard,  and  lard  oil,  and  in  the  manufacture  of  butter  substitutes. 
It  is  so  cheap  that  it  is  but  little  liable  to  adulteration,  except 
possibly  with  mineral  oils. 

Cottonseed  oil  contains  stearin,  palmitin,  olein,  and  linolin. 
A  small  proportion  of  a  hydroxy-ester  is  said  to  be  present. 

Cottonseed  Stearin. — This  is  a  commercial  name  of  the  solid 
fat  deposited  on  standing  or  by  cooling  the  oil  and  pressing. 
The  product  differs  according  to  the  completeness  with  which 
the  oil  has  been  separated.  The  proportion  of  true  stearin 
appears  to  be  very  low.  A  sample  examined  by  Hehner  & 
Mitchell  yielded  only  3  per  cent,  of  stearic  acid.  As  ordinarily 
obtained  the  fat  is  light  yellow  and  of  the  consistency  of  butter. 
It  is  largely  used  in  the  preparation  of  substitutes  for  butter 
and  lard. 

The  following  are  some  of  the  constants  of  this  fat: 

o  -a  -J.  15-5°  100°  o/r       i  o/:         100° 

Specific  gravity, ^^  =  °-9^2>  ^^o  ^  0.864  to  0.869    ^^. 

Solidifying-point, 26°  to  40°;  titer  test,  16°.     . 

Saponification  value, .  194-195. 
lodin  value, 89-104. 

Mixed  Fatty  Acids. 

Solidifying-point, 35°. 

Melting-point, 27°  to  30°. 

lodin  number, 94. 

Cottonseed  stearin  responds  to  the  color  tests  for  cottonseed 
oil. 

Another  variety  of  so-called  cottonseed  stearin  is  the  solid 
portion  of  the  fatty  acids  separated  from  the  oil  in  the  pro- 
cess of  purification  by  alkali.  It  consists  chiefly  of  stearic 
acid  and  is  employed  in  soap-making. 

MAIZE  OIL      CORN  OIL 

Maize  oil  is  obtained  by  expression  from  the  seeds  of  the 
Zea  Mays  L.,  either  directly  or  after  they  have  been  used  for 


MAIZE   OIL      CORN   OIL  1 73 

the  preparation  of  alcohol.  The  latter  product  contains  much 
free  acid.  The  most  recent  and  extended  investigation  of  this 
oil  is  that  made  by  Vult^  &  Gibson.^^  Data  furnished  by  them, 
together  with  some  from  other  sources,  have  been  incorporated 
in  the  tables  on  pages  164  and  165.  The  following  additional 
figures  are  from  their  paper. 

Acid  value, 2.25. 

Free  add  (percentage), 1.12. 

Insoluble  acid, 92.2. 

Elaidin  test, Orange-yellow  deposit. 

Bechi's  test, Dark  brown. 

Many  esters  are  present,  as  the  following  acids  have  been 
obtained  from  the  saponified  material:  Formic,  acetic,  stearic, 
palmitic,  arachidic,  hypogeic,  oleic,  HnoHc,  ricinolic  (probably), 
and,  according  to  some  investigators,  caproic,  caprylic,  and 
capric.  The  results  of  different  investigators  do  not  agree  in 
some  points.  Hehner  &  Mitchell  were  unable  to  find  stearin 
in  a  sample  examined  by  them.  J.  C.  Smith  found  volatile 
a^ids  equivalent  to  a  Reichert  number  between  2  and  3.  Hop- 
kins found  no  volatile  acids  in  the  sample  examined  by  him. 

The  oil  is  practically  without  drying  power  at  the  ordinary 
temperature.  According  to  Smith,  no  decided  siccative  prop- 
erties are  communicated  to  it  by  simply  ''boiling"  or  by  the 
addition  of  litharge.  On  passing  a  current  of  air  through  it 
for  an  hour  at  a  temperature  of  150°,  it  becomes  slightly  darker 
and  rather  more  viscous,  but  not  to  the  same  extent  as  cotton- 
seed oil.  If  to  the  oil  so  treated  a  small  quantity  of  manganese 
borate  be  added,  slight  siccative  properties  are  acquired,  and 
a  thin  film  on  lead  dries  in  from  10  to  20  hours,  but  not  com- 
pletely. Hopkins  found  that  on  heating  the  untreated  oil  in 
the  water-oven,  a  small  amount  of  oxygen  was  absorbed,  the 
increase  in  weight  amounting  to  about  i  per  cent,  at  the  end  of 
24  hours. 

The  unsaponifiable  matter  was  high  in  the  samples  exam- 


174  FOOD   ANALYSIS 

ined  by  Vulte  &  Gibson,  the  cholesterol  analog  (probably  si- 
tosterol) being  1.4  per  cent,  and  lecithin  about  i.i  per  cent. 

Gill  &  Tufts  propose  to  detect  maize  oil  in  cottonseed  oil  by 
applying  the  method  described  on  page  161.  From  known 
mixtures  of  the  two  oils,  they  obtain  the  following  weights  of 
material  the  melting-point  of  which  in  each  case  coincided 
with  that  of  sitosterol : 

Pure  cottonseed, 50  grams  yielded  0.095 

Cottonseed  45,  maize    5, "  "        0.120 

40,      "      10, "  "        0.16 

A  characteristic  reaction  of  the  oil  is  to  dissolve  it  in  carbon 
disulfid,  add  a  drop  of  sulfuric  acid  and  allow  the  mixture  to 
stand  for  24  hours,  when  it  will  become  violet. 

ARACHIS  OIL 

Arachis  oil — also  called  peanut,  ground-nut,  and  earth-nut 
oil — is  obtained  from  the  seed  of  the  Arachis  hypogcBa  L.  The 
cold  expressed  oil  from  the  first  runnings  is  nearly  colorless, 
and  that  of  the  second  expression  usually  of  a  pale  greenish- 
yellow.  It  has  an  agreeable  odor  and  flavor,  but  may  be  ob- 
tained nearly  odorless  and  tasteless.  It  contains  olein,  pal- 
mitin,  stearin,  arachin,  lignocerin,  and  probably  hypogein. 
It  is  used  as  a  salad  oil.  So-called  "peanut  butter"  consists 
simply  of  the  ground  roasted  nuts.  The  principal  use  of  the  oil 
is  as  an  adulterant  for  olive  oil.  The  specific  gravity  and  chemi- 
cal constants  of  the  two  oils  are  so  nearly  alike  that  the  detec- 
tion of  the  admixture  by  these  data  is  hardly  possible.  The 
determination  of  the  iodin  value  is  occasionally  of  use,  but  the 
only  reliable  method  is  that  of  Renard,  depending  upon  the 
estimation  of  the  amount  of  arachidic  acid,  or,  more  properly 
speaking,  of  the  arachidic  and  lignoceric  acids,  since  later  in- 
vestigation has  shown  that  the  body  separated  and  weighed 
as  arachidic  acid  consists  of  both,  lignoceric  acid  being  in  larger 
proportion.     The  method  is  laborious,  and  requires  considerable 


ARACHIS   OIL  175 

care  in  its  performance ;  many  shorter  methods  have  been  pro- 
posed, none  of  which  are  as  satisfactory  as  the  original  method, 
which  in  its  most  improved  form  is  described  by  Archbutt,  as 
follows : 

10  grams  of  the  oil  are  saponified  in  a  deep  porcelain  basin, 
using  8  c.c.  of  aqueous  sodium  hydroxid  solution  (50  grams  in 
100  c.c.)  and  70  c.c.  of  alcohol.  The  basin  is  covered,  the  mass 
gently  evaporated  to  about  20  c.c,  rinsed  with  hot  water  into 
a  separating  funnel,  mixed  with  slight  excess  of  hydrochloric 
acid,  and  shaken  with  ether  to  dissolve  fatty  acids.  Two 
extractions  are  sufficient.  After  washing  the  ether  with 
water,  it  is  distilled  in  a  250  c.c.  flask,  the  fatty  acids  dried  by 
heating  the  flask  on  a  steam-bath  and  sucking  out  the  vapor, 
and  then  dissolved  in  the  hot  flask  in  50  c.c.  of  90  per  cent, 
alcohol.  The  solution  must  not  be  allowed  to  cool  below  about 
38°,  lest  crystals  of  lignoceric  or  arachidic  acid  should  separate. 
5  c.c.  of  a  20  per  cent,  aqueous  solution  of  lead  acetate  are  added 
and  the  mixture  cooled  to  about  15°,  shaken,  allowed  to  stand 
for  half  an  hour,  washed  only  once  with  ether,  the  mass  rinsed 
back  into  the  flask  with  a  spray  of  ether,  and  digested  with 
ether  for  a  short  time;  then  again  filtered  and  again  rinsed  back. 
After  doing  this  about  four  times,  the  lead  oleate  will  be  dis- 
solved. 

The  filter  is  opened  in  a  large  plain  funnel  placed  iii  the  neck 
of  a  separating  funnel,  and  the  soaps  at  once  rinsed  into  the 
separator  with  a  jet  of  ether.  The  material  that  adheres  to 
the  paper  and  flask  is  decomposed  and  transferred  by  rinsing 
with  hot  dilute  hydrochloric  acid,  followed  by  ether.  About 
20  c.c.  of  hydrochloric  acid  (i.io  sp.  gr.)  are  poured  into  the 
separator,  shaken  well  to  decompose  the  lead  soaps,  the  aqueous 
liquid  drawn  off,  the  ether  repeatedly  washed  with  small  quan- 
tities of  cold  water  until  the  lead  chlorid  is  removed,  distilled 
in  a  250  c.c.  flask,  and  the  residual  fatty  acids  thoroughly  dried 
by  heating  on  a  steam-bath.     50  c.c.  of  ethyl  alcohol  of  exactly 


176  FOOD   ANALYSIS 

90  per  cent,  strength  (sp.  gr.  0.834)  are  poured  into  the  flask, 
which  is  then  closed  with  a  cork  carrying  a  thermometer,  heated 
cautiously  until  the  fatty  acids  have  completely  dissolved,  and 
cooled  to  15°,  when  lignoceric  and  arachidic  acids,  if  present, 
will  crystallize  out,  either  at  once  or  shortly. 

To  estimate  the  amount,  the  flask  should  be  kept  for  one 
hour,  with  occasional  agitation,  in  a  water-bath  at  either  15° 
or  20°,  or  at  some  intermediate  fixed  temperature  which  is 
nearest  to  that  of  the  laboratory,  the  crystals  collected  on  a 
small  filter,  using  only  the  filtrate  to  rinse  the  flask,  and  washed 
with  three  portions  of  10  c.c.  each  of  90  per  cent,  alcohol,  at 
the  same  fixed  temperature.  A  paper  filter  may  be  used,  but 
a  Gooch  filter,  used  with  gentle  suction,  is  better,  as  the  mother 
liquid  is  more  perfectly  removed  and  the  washing  more  thorough. 
The  filtrate  and  washings  with  90  per  cent,  alcohol  are  poured 
into  a  measuring  cylinder,  and  the  acids  thoroughly  washed 
with  70  per  cent,  alcohol,  in  which  arachidic  and  lignoceric 
acids  are  quite  insoluble,  until  some  of  the  washings  give  no 
precipitate  when  diluted  with  water.  These  washings  are 
thrown  away.  It  is  not  absolutely  necessary,  but  it  is  advisable 
to  redissolve  the  fatty  acids  thus  obtained  in  50  c.c.  of  90  per 
cent,  alcohol,  and  recrystallize  them,  filtering  and  washing  as 
before,  adding  the  filtrate  and  washings  with  90  per  cent,  alcohol 
to  the  first  quantity  in  the  measuring  cylinder.  Pure  arachidic 
and  lignoceric  acids  are  thus  obtained,  and  are  dissolved  off  the 
filter  with  boiling  ether,  distilled  down,  and  weighed  in  a  tared 
flask  after  drying  at  100°  for  an  hour.  To  the  weight  obtained 
is  to  be  added  the  amount  dissolved  by  the  90  per  cent,  alcohol, 
which  is  calculated  from  the  following  table,  based  on  deter- 
minations made  by  Tortelli  &  Ruggeri,  and  confirmed  by  Arch- 
butt.  It  will  be  noticed  that  the  amount  dissolved  varies  ac- 
cording to  the  weight  of  mixed  acids  obtained : 


SESAME   OIL  177 

Weight  of  Arachidic  and  Correction  per  100  cc  of  90  Per  Cent. 

LiGNOCERic  Acids  Alcohol  Used  for  Crystallization 

(Gram).  and  Washing  (Gram). 

(iS°  C.)  (17.5°  C.)  (20°  C.) 

0.1  or  less, 0.033  0039  0.046 

0.2 


0-3 
0.4 

0.5 
0.6 
07 
0.8 


.0.048  0.056  0.064 

.0.055  0.064  0.074 

.0.061  0.070  0.080 

.0.064  0.074  0.085 

.0.067  0.077  0.088 

.0.069  0.079  0.090 

.0.070  0.080  0.091 


0.9  and  upward, 0.071  0.081  0.091 

The  proportion  of  arachidic  and  lignoceric  acids  which  has 
been  obtained  by  different  observers  from  arachis  oil  is  very 
fairly  constant,  averaging  about  5  per  cent.,  so  that  the  amount 
of  these  acids  found  in  any  given  mixture  of  oils,  multiplied 
by  20,  will  give  a  close  approximation  to  the  amount  of  arachis 
oil  present. 

SESAME  OIL 

Sesame  oil  (also  called  Gingli  and  Teel  oil)  is  obtained  from 
the  seeds  of  the  Sesamum  orientale  L.  and  S.  indicum  L.  The 
col^  expressed  oil  is  yellow  and  of  pleasant  taste.  It  consists 
of  stearin,  palmitin,  olein,  and  linolin,  with  other  bodies  not 
clearly  understood. 

Sesame  oil  has  been  used  as  a  compulsory  addition  to  butter- 
substitutes,  in  order  to  facilitate  the  detection  of  these.  It  is 
readily  recognized  by  the  furfural  and  pyrogallol  tests. 

Adulteration. — Sesame  oil  is  liable  to  adulteration,  more 
especially  with  cottonseed,  arachis,  poppyseed,  and  rape  oils. 
These  may  be  detected  as  follows: 

Cottonseed  oil.  Halphen's,  nitric  acid,  and  Bechi's  tests; 
Livache's  test;   melting-point  of  the  fatty  acids. 

Rape  oil.  Saponification  value;  specific  gravity;  solidifying 
and  melting  points  of  the  fatty  acids. 

Poppyseed  oil.     lodin  value;  temperature  reactions. 

Arachis  oil.  Specific  gravity;  determination  of  arachidic 
acid. 


178  FOOD   ANALYSIS 

RAPE  OIL 

Rape  oil  is  obtained  from  several  varieties  of  the  Brassica 
campestris  L.  The  oils  derived  from  all  of  these  are,  as  a  rule, 
described  indiscriminately  rape  oil  or  colza  oil;  but  on  the 
continent  of  Europe- ''colza  oil"  is  sometimes  taken  to  mean 
only  that  from  a  particular  variety  (napus).  The  physical  and 
chemical  characters  of  all  the  varieties  appear  to  be  practically 
identical. 

Rape  oil  is  pale  yellow,  has  a  peculiar  smell,  and  rather  an 
unpleasant  taste.  It  consists  chiefly  of  stearin,  olein,  and 
erucin.  It  also  contains  a  small  proportion  of  arachidin. 
About  0.4  per  cent,  of  arachidic  acid  is  said  to  have  been  sepa- 
rated from  it.  It  is  very  Hable  to  adulteration,  but  is  of  interest 
here  only  as  an  adulterant  of  olive  oil.  The  physical  and 
chemical  characters  are  given  in  the  tables  on  pages  164  and  165. 

Palas^  test. — A  dilute  solution  of  fuchsin  (about  i  per  cent.) 
and  a  strong  solution  of  sodium  acid  sulfite  (about  30  per  cent.) 
are  prepared  separately.  20  c.c.  of  each  of  these  are  mixed, 
200  c.c.  of  water  added  and  5  c.c.  of  strong  sulfuric  acid.  When 
the  solution  is  decolorized,  10  c.c.  of  the  sample  should  be 
shaken  with  it.  A  partial  restoration  of  color  will  occur  if 
rape  oil  be  present.  It  will  be  well  to  shake  in  a  vessel  full  of 
the  mixture,  as  contact  of  air  may  produce  color.  It  must  also 
be  borne  in  mind  that  several  aldehydes,  especially  formalde- 
hyde, will  produce  color  with  this  test. 

COCONUT  OIL 

Coconut  oil  is  obtained  from  kernels  of  the  coconut  (species 
of  Cocos),  being  usually  expressed  with  aid  of  heat.  It  is  nearly 
white  and  about  the  consistency  of  butter;  has  the  taste  and  odor 
of  the  coconut.  It  contains  palmitin  and  stearin,  much  myristin 
and  laurin,  with  some  caprin,  caproin,  and  caprylin.  It  gives, 
therefore,  a  notable  amount  of  volatile  acids  and  soluble  acids. 


CACAO-BUTTER  1 79 

By  treatment  with  alcohol  and  animal  charcoal,  a  white  neutral 
product  of  agreeable  flavor  and  good  keeping  qualities  is  ob- 
tained which  is  sold  for  food  purposes  under  fanciful  names, 
such  as  "vegetable  butter,"  ''vegetaline,"  ''laureol,"  ''nuco- 
line."  By  submitting  the  oil  to  pressure  products  termed 
"coconut  olein"  and  "coconut  stearin"  are  obtained.  From 
samples  of  these,  Allen  has  obtained  the  following  data : 

Sp.  Gr.  (water  at  15.5°=  i)  Solidifying-  Melting-    Reichert 

AT  15.5°;        AT  98-99°.       .  POINT.  POINT.  NuMBER. 

Olein, 0.926         0.871  4  rising  to  8  5.6 

Stearin, solid  0.869  21.5  rising  to  26  28.5  3.1 

For  its  recognition,  the  Reichert-Meissl  number  is  most 
satisfactory.     (See  the  constants  on  page  165.) 

CACAO-BUTTER 

Cacao-butter  is  the  fat  expressed  from  cacao  beans.  It  is 
yellowish-white,  becoming  paler  on  keeping,  possesses  the 
pleasant  odor  and  flavor  of  chocolate,  is  solid  at  ordinary  tem- 
peratures, but  easily  melts  in  the  mouth.  It  consists  chiefly  of 
ste^arin,  palmitin,  and  laurin,  with  small  proportions  of  arach- 
idin,  linolin,  formin,  acetin,  and  butyrin.  It  is  insoluble  in  90 
per  cent,  alcohol,  but  dissolves  in  5  parts  of  boiling  absolute 
alcohol. 

Adulteration. — The  common  adulterants  of  cacao-butter 
are  tallow,  stearic  acid,  lard,  paraffin  wax,  beeswax,  coconut 
and  arachis  oils.  The  constants  will  usually  suffice  for  their 
detection. 

Stearic  acid  is  indicated  by  the  high  acid  value ; 

Paraffin  or  beeswax^  by  the  low  saponification  value  and 
high  proportion  of  unsaponifiable  matter; 

Vegetable  oils,  by  the  increased  iodin  value  and  lower  melt- 
ing-point of  the  fatty  acids; 

Coconut  oil  by  the  low  iodin  value,  high  saponification  value, 
and  moderately  high  Reichert  number. 

The  following  special  tests  are  also  useful: 


l8o  FOOD   ANALYSIS 

Bjorkland^s  test. — 3  grams  of  the  fat  are  mixed  in  a  test- 
tube  with  6  grams  of  ether,  the  test-tube  closed  with  a  cork, 
and  solution  effected,  if  possible  by  shaking.  When  wax 
is  present,  a  cloudy  liquid  results  which  is  not  changed  on 
warming.  If  the  solution  is  clear,  the  tube  is  placed  in  melting 
ice  and  the  time  observed  after  which  the  solution  begins  to 
become  milky  or  to  deposit  white  flakes;  then  the  temperature 
is  noted  at  which  the  mixture  becomes  clear  on  removing  from 
the  ice-water.  Pure  cacao-butter  solution  becomes  cloudy  in 
10  or  15  minutes,  and  becomes  clear  again  at  19°  to  20°.  With 
cacao-butter  containing  5  per  cent,  of  tallow,  these  figures 
are  8  minutes  and  22°  respectively;  10  per  cent,  of  tallow,  7 
minutes  and  25°. 

Filsinger  suggests  a  modified  ether  test:  2  grams  of  the  fat 
are  melted  in  a  graduated  tube  with  6  c.c.  of  a  mixture  of  4 
volumes  of  ether  (sp.  gr.  0.725)  and  2  volumes  of  alcohol  (sp. 
gr.  0.810),  shaken,  and  set  aside.  The  pure  fat  gives  a  solution 
that  remains  clear,  even  on  cooling  to  0°. 

Hager  recommends  the  following  test:  About  i  gram  of 
the  fat  is  warmed  with  2  to  8  grams  of  anilin  until  dissolved; 
the  mixture  is  allowed  to  stand  one  hour  at  15°  or  one  and  a 
half  hours  at  17°  to  20°.  Pure  cacao-butter  floats  as  a  liquid 
layer  on  the  anilin.  If  the  sample  contain  tallow,  stearic  acid, 
or  a  Httle  paraffin,  particles,  which  remain  hanging  on  the  upper 
wall  on  gentle  agitation,  are  formed  in  the  oily  layer.  If  wax 
or  much  paraffin  be  present,  the  layer  solidifies.  If  much 
stearic  acid  be  present,  layers  will  not  form,  but  the  whole  will 
solidify  to  a  crystalline  mass.  The  oily  layer  from  pure  cacao- 
butter  hardens  only  after  many  hours.  A  parallel  test  should 
be  made  with  a  sample  of  known  purity. 

LARD 

Strictly  speaking,  lard  is  the  fat  obtained  from  the  mem- 
branes about  the  kidneys  and  intestines  of  the  common  hog. 


LARD  l8l 

Commercial  lard  consists  of  the  mixed  fat  from  various  parts 
of  the  animal. 
U.S.  Standard. 

Lard  is  the  rendered  fresh  fat  from  slaughtered,  healthy 
hogs,  free  from  rancidity,  and  containing  not  more  than  i 
per  cent,  of  substances  not  fat  (other  than  fatty  acids), 
necessarily  incorporated  in  the  process  of  rendering. 

Leaf  lard  is  the  lard  rendered  at  moderately  high  tempera- 
tures from  the  internal  fat  of  the  abdomen  of  the  hog,  excluding 
that  adherent  to  the  intestines,  and  has  an  iodin  number  not 
greater  than  60. 

Neutral  lard  is  lard  rendered  at  low  temperature. 

The  following  grades  have  also  been  given,  but  are  not 
included  in  the  official  definitions.  The  requirement  of  not 
over  60  for  iodin  number  of  standard  lard  seems  somewhat 
severe. 

Choice  Kettle-rendered  Lard. — Choice  Lard. — Portions  of  the 
leaf,  together  with  the  fat  cut  from  the  backs,  are  rendered  in 
steam- jacketed  open  kettles.  The  hide  is  removed  from  the 
back-fat  before  rendering. 

Prime  Steam  Lard. — The  whole  head  of  the  hog,  after  the 
removal  of  the  jowl,  is  used  for  rendering.  The  fat  from  the 
small  intestines  and  fat  attached  to  the  heart  are  afso  used. 
The  back-fat  and  trimmings  and  the  leaf  may  also  be  used. 
Prime  steam  lard,  therefore,  may  represent  the  fat  of  the  whole 
animal,  or  only  portions. 

A  lower  grade  is  made  from  intestines.  The  definition  of 
the  term  as  used  by  hog-packers  is:  everything  inside  of  a 
hog  except  the  lungs  and  the  heart,  or,  in  other  words,  the  ab- 
dominal viscera. 

Lard  consists  of  stearin,  palmitin,  and  olein,  with  a  small 
amount  of  linolin.  Hehner  &  Mitchell  obtained  stearic  acid 
in  proportions  varying  from  6  to  16  per  cent.  The  unsaponifi- 
able  matter  is  small;  Allen  &  Thomson  found  0.23  per  cent. 


1 82  FOOD   ANALYSIS 

American  and  European  lards  differ  appreciably  in  some 
analytic  characters,  as  exhibited  in  the  following  table : 

Sp.  Gr.  —  --•      lODiN  Number. 
15° 

American  Lards: 

From  head, 0.8632  65.9 

"     back, 0.8616  63.8 

"     leaf, 0.8626  61 .4 

European  Lards: 

From  back, 0.8607  60.5 

"     kidney, 0.8590  52.6 

"     leaf, 0,8588  53.1 

More  marked  differences  in  the  iodin  value  of  fat  from  dif- 
ferent parts  of  the  animal  have  been  noted  by  other  observers. 

Fresh  lard  usually  contains  little  free  acid,  generally  from 
0.1  to  0.4  per  cent.,  but  the  proportion  may  rise  above  i  per 
cent.  On  exposure  to  the  air  the  amount  increases  consider- 
ably. Spaeth  has  made  a  number  of  determinations  of  free 
acid  of  samples  kept  in  loosely-corked  flasks.  The  following  is 
a  summary  of  the  results  obtained : 

Fresh.  i  Year  Old.        3  Years  Old. 

Free  acid  calculated  as  oleic, . .    0.013  to    0.45      0.51  to    6.05       2.81014.2 
Iodin  number, 63.2      to  51.7      55.4    1036.7       41.11021.5 

Adulteration. — Lard  is  much  adulterated,  especially  with 
cottonseed  oil,  cottonseed- stearin,  beef- stearin,  and  excess  of 
water.  Articles  containing  no  lard  have  often  been  sold  under 
the  name  ''refined  lard."  More  recently  such  preparations 
have  been  designated  "lard  compound"  or  "compound  lard." 
Maize,  sesame,  and  arachis  oils  may  be  present  in  these  articles. 
Much  attention  has  been  given  to  the  examination  of  com- 
mercial lards,  and  the  following  is  a  summary  of  the  more 
trustworthy  of  the  methods.  A  comparison  of  constants  will 
be  found  on  pages  164  and  165. 

Specific  Gravity. — The  specific  gravity  of  lard  is  usually  be- 
tween 0.860  and  0.861.      The  usual  adulterants,  except  beef- 


LARD  183 

stearin,  tend  to  raise  the  specific  gravity,  but  they  may  be 
corrected  by  addition  of  vegetable  oils.  Wainwright  ob- 
tained valuable  data  by  compressing  the  sample  in  muslin  or 
linen  at  ordinary  temperatures  and  examining  the  more  fluid 
portion. 

Melting-point. — This  datum  is  usually  of  Httle  value.  Goske 
obtained  some  useful  results  by  applying  the  titer-test  (p.  11). 
Pure  lards  gave  figures  ranging  from  23°  to  30°;  lard  adul- 
terated with  tallow  and  lard  oil,  from  29.7°  to  36°.  The  solidi- 
fying-point  of  the  fatty  acids  may  be  of  value  in  detecting  maize 
oil. 

lodin  Number. — This  differs  considerably  according  to  the 
part  of  the  animal  from  which  the  sample  is  derived.  The 
following  table  has  been  compiled  from  the  results  of  many 
observers: 

American  Lards. 

Head, 63.    to  85 ;      average,  75. 

Foot, 63,    to  77 ;      average,  70. 

Ham, 66.    to  69 ;      average,  67.8. 

Back,.. 61. 5  to  66.7;  average,  64.1. 

Leaf, 52.51066.7;  average,  59.6. 

Intestines, 60. 

English  lards  may  give  figures  6  or  8  units  lower. 

American  steam-lard  derived  from  different  parts  of  the 
animal  has  an  iodin  value  of  about  59  to  66,  but  the  effect  of 
age  on  this  must  not  be  forgotten  (see  page  182).  As  a  rule, 
the  iodin  value  of  mixtures  of  lard,  beef-stearin,  and  lard  oil 
is  well  within  these  limits,  so  that  normal  iodin  value  is  not 
proof  of  purity.  The  addition  of  vegetable  oils  raises  the  figure 
notably,  but,  according  to  Lewkowitsch,^^  the  iodin  value  of  the 
liquid  fatty  acids  is  the  best  method  of  detecting  admixture 
of  vegetable  fats.  With  American  lard,  the  figure  is  between 
97  and  106;  and  with  European  lards,  between  90  and  96. 
Should  a  sample  give  a  value  within  the  above  limits,  it  must 


184  FOOD   ANALYSIS 

be  further  examined  for  beef- stearin  and  coconut  oil,  since 
these  may  be  added  with  a  vegetable  oil  to  bring  the  figure 
within  the  limits  of  normal  lard. 

Thermal  Test. — The  rise  of  temperature  with  sulfuric  acid, 
and  more  especially  the  heat  of  bromination,  is  of  service  in 
the  detection  of  cottonseed  products.  The  results  with  Mau- 
mene's  test,  as  reported,  differ  greatly.  It  is  advisable  to  per- 
form tests  with  samples  of  pure  lard  and  cottonseed  oil  side 
by  side  with  the  suspected  sample.  The  initial  temperature 
may  be  about  35°  or  40°.  Care  should  be  taken  that  the  sample 
contains  no  water. 

Rejractometric  Examination. — The  examination  of  lard  by 
the  refractometer  or  the  butyrorefractometer  is  of  value.  Vege- 
table oils  are  readily  detected,  but  the  indications  in  the  case 
of  beef  tallow  and  stearin  are  not  so  satisfactory.  According 
to  Jean,  better  results  are  obtained  by  operating  on  the  liquid 
fatty  acids.  The  following  table  is  compiled  from  the  results 
of  Jean,  Dupont,  and  other  observers.  The  figures  were  obtained 
by  means  of  a  refractometer  different  from  those  figured  on 
page  154,  but  the  table  has  value  for  the  comparative  results. 
The  liquid  fatty  acids  may  be  prepared  as  described  on  page 
141.  Jean,  whose  figures  are  given  in  the  table,  prepared  them 
by  Sear's  process:  50  grams  of  the  lard  are  saponified,  the 
fatty  acids  separated  by  addition  of  acid,  washed  with  hot 
water,  and  mixed  in  a  flask  together  with  250  c.c.  of  carbon 
disulfid  and  8  to  10  grams  of  zinc  oxid.  The  zinc  salts  of  the 
liquid  fatty  acids  dissolve  in  the  carbon  disulfid,  and  can  thus 
be  separated  from  the  solid  fatty  acids.  The  carbon  disulfid 
is  evaporated,  the  fatty  acids  liberated  with  hydrochloric 
acid,  well  washed  with  hot  water,  and  dried  at  a  temperature 
of  120°. 


LARD  185 

Degrees  in  Oleoreiractometer. 

P  .  Liquid  Fatty 

Acids. 

American  lard,  mixed, _  7 

"     leaf, _ii.5 

"  "     foot,  back,  head,  etc., —    4  to— 11 

European    "      —12  to— 13  —30 

"  "     stearin, —  10  to  —  1 1 

Beef  tallow, —  16  to  —  1 7  —  40 

"    stearin, _  34 

Veal       "       -19 

Coconut  oil, —  54 

Cottonseed  oil, +  1 2  to  +  23 

usually  4-  20  +10 

"           stearin, +25  +20 

Arachis  oil, +3.5  to  +  7  —  15 

Sesame    " +  13  to  -|- 18  —  18 

European  lard  with  20  per  cent,  cottonseed  oil, —  6 

"  "      "     10        "  "         stearin, —7 

u  u        cc       30  "  "  "  ..  _3 

<c  "        50  "  "  "  ..  +1 

"  "      "     20        "        sesame  oil, —20 

'     "  "      "     20        "        arachis   "   —8  —23 

"  "      "     50        "        beef  tallow, —14  —33 

"  "    40;  beef  fat,  40;   cottonseed  oil,  20  per 

cent., —  24 

European  lard  60;  mutton  tallow,  25;  arachis  oil,  15 

percent., —13  —22 

European  steam  lard,  60;  beef  tallow,  15;  arachis  oil, 

25  per  cent., _  8 

Special  Tests. 

Seed  Oils  (cottonseed,  sesame,  arachis,  and  maize);  iodin 
number  of  the  liquid  fatty  acids.  Separation  of  cholesterol 
analogs.     The  oils  are  further  specifically  identified  as  follows : 

Cottonseed  Oil. — Lard  from  animals  fed  liberally  on  cotton- 
seed products  may  give  faint  reactions  for  cottonseed  oil  by  the 
qualitative  tests.  Halphen's  test  is  the  most  satisfactory.  The 
nitric  acid  and  Bechi's  tests  may  also  be  applied.  Pure  lard 
17 


i86 


FOOD   ANALYSIS 


that  has  been  exposed  to  the  air  may  respond  to  Bechi's  test, 
so  that  the  sample  should  be  carefully  taken  from  the  interior 
of  the  mass.  On  the  other  hand,  cottonseed  oil  that  has  been 
heated  for  a  short  time  to  240°  no  longer  responds  to  this  test, 
and  reacts  to  Halphen's  test  with  diminished  intensity. 

Jones  suggested  sulfur  chlorid  as  a  test  for  cottonseed  oil, 
which  forms  with  it  a  hard  mass  partly  insoluble  in  carbon 
disulfid.  Lewkowitsch  has  found  the  method  useful,  and  ap- 
plies it  as  follows:  5  grams  of  the  fat  are  dissolved  in  2  c.c. 
of  carbon  disulfid,  2  c.c.  of  sulfur  chlorid  are  added,  and  the 
mixture  heated  on  the  water-bath.  The  following  results  were 
obtained  with  mixtures  of  lard  and  cottonseed  oil : 


Cottonseed  Oil  Per- 
centage. 

None, No  reaction 

10 Thickens    after  35  minutes. 


20. 
30- 
40. 

5° 
60. 
70. 
80. 
90. 
100. 


Sol 


d  after 


Solubility  of  Product 

IN  Carbon  Disulfid. 

Completely  soluble. 

35  minutes. 

iC                           u 

30 

52.0  per  cent,  soluble. 

26        " 

39.6        " 

18 

34.8        " 

10  minutes. 

8 

37.4  per  cent,  soluble. 

7        " 

30.6        " 

6 

32.6 

4        " 

30.0 

3        " 

24.0 

It  is  recommended  to  test  the  sample  side  by  side  with  pure 
lard,  or  with  mixtures  of  known  composition. 

Cottonseed  Stearin. — For  the  detection  of  this  the  above  tests 
for  cottonseed  oil  should  be  applied,  also  specific  gravity  de- 
termination. 

Arachis  Oil. — Renard's  method  should  be  applied  (page  175). 

Sesame  Oil. — Furfural  and  pyrogallol  tests  should  be  applied 
(page  165). 

Maize  Oil. — In  the  absence  of  other  seed  oils,  the  melting- 
point  of  the  mixed  fatty  acids  is  of  use. 


LARD  1B7 

Coconut  Oil. — The  iodin  number,  saponification  value,  and 
Reichert  number  are  useful  data. 

Tallow. — Beej-stearin. — Belfield  proposed  to  use  the  follow- 
ing: The  sample  is  dissolved  in  warm  ether  and  the  solution 
is  cooled  slowly  and  the  crystals  deposited  are  examined  under 
the  microscope.  Crystallization  should  take  place  as  slowly 
as  possible.  A  good  method  is  to  place  a  cotton  plug  in  the 
mouth  of  the  tube,  and  allow  the  ether  to  evaporate  slowly. 
The  crystals  from  pure  lard  are  usually  in  the  form  of  plates 
with  oblique  terminals. 

Cochran  finds  the  following  method  satisfactory: 

2  c.c.  of  the  melted  fat  are  mixed  with  22  c.c.  of  fusel  oil 
and  the  mixture  warmed  to  about  blood  heat,  and  when  com- 
plete solution  is  effected  it  is  allowed  to  cool  slowly  to  16°  or 
17°  and  maintained  at  this  temperature  for  several  hours,  dur- 
ing which  a  crystalline  deposit  forms.  This  is  transferred  to 
a  filter,  the  fusel  oil  drained  off  as  far  as  possible,  and  a  part 
or  whole  of  the  residue  dissolved  in  ether  in  a  test-tube,  the 
mouth  of  the  tube  being  plugged  with  cotton.  The  crystals 
which  form  on  standing  may  be  mounted  in  cottonseed  oil 
and  examined  under  a  microscope. 

The  proportion  of  beef- stearin  present  may  be  approxi- 
mately estimated  by  Stock's  modification  of  Belfield's  test. 
It  consists  in  comparing  the  crystals  obtained  from  an  ethereal 
solution  with  those  from  two  standard  sets  of  mixtures,  the  first 
consisting  of  pure  lard  melting  at  34°  to  35°,  with  5,  10,  15, 
and  20  per  cent,  of  beef-stearin  melting  at  56°;  the  second  of 
pure  lard,  of  melting-point  of  39°  to  40°,  with  5,  10,  15,  and  20 
per  cent,  of  beef-stearin  melting  at  50°.  The  process  is  as  fol- 
lows: The  melting-point  of  the  sample  is  determined  by  the 
capillary  tube  method.  Suppose  the  melting-point  be  found 
at  34°,  3  c.c.  of  the  melted  fat  are  run  into  a  graduated  cylinder 
of  about  25  c.c.  capacity;  21  c.c.  of  ether  are  added,  and  the 
fat  dissolved  at  20°  to  25°;  3  c.c.  of  each  of  the  first  set  of  mix- 


1 88  FOOD   ANALYSIS 

tures  are  treated  in  exactly  the  same  way.  The  five  cyhnders 
are  cooled  down  to  13°,  and  allowed  to  remain  at  that  tem- 
perature for  24  hours.  An  approximate  estimate  as  to  the 
amount  of  the  adulterant  is  arrived  at  by  reading  off  the  ap- 
parent volume  of  the  deposited  crystals.  The  ether  is  then 
poured  off  as  far  as  possible,  and  10  c.c.  of  fresh  ether  at  13° 
are  added  in  each  case.  The  cylinders  are  again  shaken,  cooled 
as  before,  and  the  proportion  of  crystals  read  off  as  before. 
Finally,  the  contents  are  emptied  into  weighed  shallow  beakers, 
the  ether  drained  off  carefully,  the  mass  allowed  to  dry  for  15 
minutes  at  100°,  and  weighed.  The  weight  obtained  for  the 
sample  under  examination  is  compared  with  the  weight  of  the 
crystals  obtained  from  the  standard  nearest  to  it.  The  second 
set  of  mixtures  is  used  for  samples  of  higher  melting-point. 
The  actual  presence  of  beef-fat  must  be  proved  by  microscopic 
examination,  when  the  characteristic  tufts  are  seen.  No 
sample  of  pure  lard  melting  below  39°  yielded  more  than  o.oi  i 
gram  of  crystals  under  the  above  conditions.  A  sample  of  the 
melting-point  45.8°  gave,  however,  0.146  gram  of  crystals. 

Beef-fat  crystallizing  from  ether  forms  spherical  masses, 
which  when  pressed  under  a  cover-glass  become  fan-shaped 
tufts.  Under  high  magnification  the  individual  crystals  still 
appear  in  needle-like  form  quite  distinct  from  the  plates  pro- 
duced by  lard.  In  samples  of  lard  containing  beef-fat  the 
crystals  obtained  are  not  a  mixture  of  those  typical  of  the  two 
substances,  but  usually  uniform  and  resemble  those  of  lard 
somewhat  modified.  In  some  cases  the  manner  of  aggregation 
is  similar  to  that  of  beef-fat  crystals,  but  the  individual  crys- 
tals, instead  of  being  needle-shaped,  have  more  the  appearance 
of  those  from  lard.  It  will  often  be  necessary  to  recrystallize 
repeatedly  under  varying  conditions,  to  get  characteristic  crys- 
tals. 


BUTTER-FAT  1 89 

BUTTER-FAT 

The  fat  of  cow's  milk  is  the  only  one  of  importance,  and 
this  is  only  known  commercially  in  the  form  of  butter,  a  mix- 
ture of  the  fat  with  varying  proportions  of  water,  salt,  curd, 
coloring-matter,  sometimes  boric  acid,  and  other  fats.  For 
methods  of  analysis  and  distinction  of  butter-fat  from  other 
fats,  see  under  "Milk  Products." 


MILK  AND  MILK  PRODUCTS 

Milk,  the  nutritive  secretion  of  nursing  mammals,  consists 
of  water,  fat,  proteids,  sugar,  and  mineral  matters.  Cow's 
milk  is  meant  in  all  cases,  unless  otherwise  stated. 

Fat. — This  occurs  in  globules  varying  from  0.0015  ^^-  to 
0.005  mm.  in  diameter,  in  a  condition  which  prevents  spon- 
taneous coalescence.  It  is  peculiar  among  animal  fats  in  con- 
taining a  notable  proportion  of  acid  radicles  with  a  small  num- 
ber of  carbon  atoms. 

Proteids. — The  nature  of  the  proteids  of  milk  has  been 
much  discussed,  but  it  is  now  generally  conceded  that  there  are 
at  least  three  forms,  casein,  albumin,  and  globulin,  the  casein 
being  present  in  by  far  the  greatest  amount,  and  the  globulin  as 
traces  only. 

Casein. — Casein  is,  probably  in  part,  in  combination  with 
phosphates.  It  is  precipitated  by  many  substances  among 
which  are  acids,  rennet,  and  magnesium  sulfate,  but  not  by 
heat.  Acids  precipitate  it  by  breaking  up  the  combination 
with  phosphates.  The  action  of  rennet  is  complex  and  probably 
partly  hydrolytic,  splitting  the  casein  into  several  proteids,  some 
of  which  are  precipitated  in  the  curd.  .  Films  of  proteid  matter 
occur  abundantly  in  milk,  for  which  reason  it  is  distinctly 
opaque,  even  when  nearly  all  the  fat  has  been  removed  by 
centrifugal  action. 

The  albumin  of  milk  appears  to  be  a  distinct  form,  and  is 
called  lactalbumin.  It  is  not  precipitated  by  dilute  acids,  but 
is  coagulated  by  heating  to  70° — 75°.  The  proportion  in  cow's 
milk  is  usually  from  0.35  to  0.50  per  cent.,  but  colostrum  may 
contain  much  larger  proportions. 

Globulin  is  present  only  in  minute  amounts  in  normal  milk, 

190 


MILK   AND  MILK  PRODUCTS  19I 

but  colostrum  may  contain  as  much  as  8  per  cent.  It  is  co- 
agulated on  heating. 

Lactose. — This  is  a  sugar  peculiar  to  milk. 

Citric  acid  is  a  normal  constituent  of  the  milk  of  various 
animals.  In  human  milk,  the  quantity  is  about  0.5  gram  to 
the  liter;  in  cow's  milk,  from  i  to  1.5  grams.  It  is  not  de- 
pendent on  the  citric  acid  present  in  the  food. 

Wender  states  that  the  following  enzyms  exist  in  normal  milk: 

Milk  trypsin  or  galactase.  This  is  a  proteolytic  enzym.  It 
dissolves  casein  and  is  rendered  inactive  by  exposure  to  a  tem- 
perature of  76°. 

Milk-catalase.  This  can  decompose  hydrogen  dioxid  and 
similar  compounds.  It  is  rendered  inactive  by  exposure  to  a 
temperature  of  80°. 

Milk-peroxydasCy  an  anerobic  oxydase,  that  is,  a  body  that 
has  the  power  to  decompose  peroxids  and  carry  the  oxygen 
over  to  other  substances.  This  is  the  substance  which  produces 
the  reaction  when  milk,  hydrogen  dioxid  and  tincture  of  guaia- 
cum  are  mixed,  by  which  a  deep  blue  is  obtained.  This  enzym 
is  rendered  inactive  by  exposure  to  a  temperature  of  83°. 

Minute  amounts  of  nitrogenous  bases  occur  in  milk. 

Mineral  Matter. — The  ash  of  milk  contains  calcium,  mag- 
nesium, iron,  potassium,  and  sodium  as  chlorids,  carbonates, 
sulfates,  and  phosphates.  It  does  not  exactly  represent  the 
salts  present  in  milk. 

Richmond  has  determined  the  ratio  of  the  ash  to  the  solids 
not  fat  of  135  samples  of  milk.  This  was  found  to  range  from 
7.8  to  9.4  per  cent.,  but  more  usually  from  7.8  to  8.5  (average 
8.2)  per  cent.  Many  ashes  were  alkaline  to  turmeric,  litmus, 
and  phenolphthalein,  the  maximum  alkalinity  being  0.025  P^^* 
cent,  calculated  as  sodium  carbonate. 

The  following  table  gives  the  approximate  composition  of 
some  milks.  Analyses  of  the  milks  of  less  important  animals 
have  been  published,  but  the  figures  are  of  uncertain  value,  be- 


192  FOOD   ANALYSIS 

cause  it  is  not  sure  that  the  samples  were  of  average  character 
or  the  methods  of  analysis  accurate : 

Human.  Cow.  Mare.  Goat.  Ass.  Gamoose. 

Fat, 3.5  4.0  I.I  4.3  1.6  5.6 

Sugar, 6.8  4.8  6.6  4.0  6.1  5.4 

Proteids, 1.5  3.5  1.9  4.6  2.2  3.8 

Ash, 0.2  0.7  0.3  0.6  0.5  i.o 

12.0  13.0  9.3  13.5  10.4         15.8 

Normal  milk  is  an  opaque  white  or  yellowish-white  fluid, 
with  an  odor  recalling  that  of  the  animal,  and  a  faint  sweet 
taste.  The  opacity  is  due  largely  but  not  entirely  to  the  fat 
globules.  The  reaction  of  freshly  drawn  milk  to  litmus  is 
usually  alkaline,  but  is  sometimes  amphoteric;  that  is,  it  turns 
the  red  paper  blue  and  the  blue  paper  red.  The  specific  gravity 
varies  between  1.027  ^-nd  1.035.  I^  usually  undergoes  a  gradual 
augmentation  (sometimes  termed  Recknagel's  phenomenon) 
for  a  considerable  time  after  the  sample  has  been  drawn.  The 
increase  may  amount  to  two  units  (water  being  1000).  The 
specific  gravity  becomes  stationary  in  about  5  hours  if  the  milk 
be  maintained  as  a  temperature  below  15°,  but  at  a  higher 
temperature  it  may  require  24  hours  to  acquire  constancy.  The 
change  is  not  entirely  dependent  on  the  escape  of  gases. 

Unless  collected  with  special  care  and  under  conditions  of 
extreme  cleanliness,  milk  always  contains  many  bacteria  and 
animal  matter  of  an  offensive  character,  such  as  epithelium, 
blood  and  pus  cells,  particles  of  feces,  and  soil. 

At  ordinary  temperature  milk  soon  undergoes  decomposition, 
by  which  the  milk  sugar  is  converted  principally  into  lactic  acid, 
and  the  proteids  partly  decomposed  and  partly  coagulated. 
The  liquid  becomes  sour  and  the  fat  is  inclosed  in  the  coagu- 
lated casein.  In  the  initial  stages  of  decomposition  the  proteids 
frequently  undergo  transformations  into  substances  which  are 
the  cause  of  the  violent  poisonous  effects  occasionally  produced 
by  ice-cream  and  other  articles  of  food  into  the  preparation  of 
which  milk  enters. 


MILK   AND   MILK   PRODUCTS  1 93 

Boiling  produces  coagulation  of  the  albumin,  some  caramel- 
ization  of  the  sugar,  and  develops  a  greater  facility  of  coales- 
cence on  the  part  of  the  fat  globules.  Enzyms  are  rendered 
inert  and  most  microbes  are  killed. 

When  milk  is  allowed  to  stand,  some  of  the  fat  rises  gradually 
and  forms  a  rich  layer,  constituting  cream.  The  proportion 
of  cream  depends  on  several  conditions.  The  amount  formed 
in  a  given  time  cannot  be  taken  as  a  measure  of  the  richness  of 
the  milk.  Water  added  to  milk  causes  a  more  rapid  separation 
of  the  cream.  Centrifugal  action  separates  nearly  all  of  the 
fat.  The  following  figures,  given  by  D'Hout  as  averages, 
show  this  effect : 

Whole  Milk.     Separated  Milk.      Cream. 

Specific  gravity,    1032  1034  1015 

Total  solids, 14.10  9.6  26.98 

Sugar, 470  5-05  3-32 

Casein, 3.50  3.62  2.02 

Ash, 0.79  0.78  0.58 

Fat, 5.05  0.20  21.95 

Buttermilk  is  the  residue  after  removal  of  the  butter  by  churn- 
ing-.    Vieth  gives  the  following  analyses: 

Total  Solids.  Fat.  Solids  not  Fat.  Ash. 

9.03  0.63  8.40  0.70 

8.02  0.65  7.37  1.29 

10.70  0.54  10.16  0.82 

Whey  or  Milk-serum  is  the  liquid  freed  from  curd  after 
precipitation  by  rennet  or  acids.  In  most  cases  it  contains  a 
notable  amount  of  proteids,  as  shown  in  the  following  analyses 
by  Cochran : 

Milk.  Whey. 

Total  solids.                Solids  not  fat.                        Total  solids.  Proteids  removed . 

9.27  9.13  6.62  2.51 

9.27  9.13  6.1  3.03 

14.05  8.35  6.62  2.33 

7.71  7.61  5.98  1.63 

8.91  8.71  6.50  2.21 
18 


194  FOOD   ANALYSIS 

The  whey  of  any  given  milk  has  practically  the  same  com- 
position, whether  taken  from  the  original  milk,  skimmed  milk, 
or  cream. 

Average  Proportion  oj  Solids  in  Milk. — The  most  extensive 
data  on  this  point  are  those  obtained  by  Vieth.  The  total 
number  of  samples  was  120,540.  The  averages  of  the  entire 
series  are  as  follows : 

Fat, 4.1  per  cent. 

Non-fatty  solids, 8.8 

Total  solids, 12.9       " 

Richmond's  results  for  several  years  have  confirmed  these 
figures. 

Seasonal  Variations  in  the  Composition  of  Milk. — The  poor- 
est quality  usually  occurs  during  the  first  half  of  the  year,  es- 
pecially in  April.  A  low  figure  is  also  frequently  noted  about 
July.  In  autumn  the  quality  rises,  being  highest  in  October 
and  November. 

Deficient  Solids. — The  following  are  some  instances  of  de- 
ficiency of  solids  in  milk  known  to  be  genuine : 

Total 
Sp.  Gr.  Fat.  S.  N.  F.  Solids.  Analyst. 

1029.6           3.38  7.95  ^'^•33  Cochran. 

1030.0            3.62  8.31  11-93  Cochran. 

1029.3            3.63  8.02  11-65  Cochran. 

—               3.99  8.36  12.35  Leffmann  and  Beam 

3. II  8.33  11-44)  Monthly  averages  N. 

305  8.33  11-38  [  J.    State    Agricul- 

3.23  8,44  11.67)  tural  Exp.  Station. 

The  following  analyses  of  milk  from  individual  cows  were 
made  by  Cochran.  The  samples  were  taken  under  precau- 
tions which  insured  their  genuineness.  The  data  are  all  direct 
determinations.  The  total  solids  were  obtained  by  drying  in 
the  usual  manner,  and  the  fat  by  the  L-B.  method.  Low  milks 
have  been  often  noted  in  the  vicinity  of  Philadelphia. 


MILK   AND   MILK   PRODUCTS  I95 

Sp.  Gr.  Fat.  S.  N.  F.  Total  Solids. 

1026.6  2.35  6.78                              9.13 

1028.8  2.95  7.56                             10.51 

1028.8  2.40  7.56                              9.96 

1033.5  2.90  8.68                          11.58 

The  mixed  milk  from  a  herd  of  any  considerable  number  will 
rarely,  if  ever,  show  a  proportion  of  non-fatty  solids  less  than 
8.5  per  cent,  nor  less  than  3.5  per  cent,  of  fat.  Cochran  ex- 
amined the  milk  from  each  cow  of  a  herd  of  59,  with  the  follow- 
ing results: 

Fat, 2.60  to    5.40. 

Total  solids, 9.86  to  13.78. 

The  average  milk  of  the  entire  herd  was: 

Fat, 3.76  per  cent. 

Total  solids, 12.33  P^r  cent. 

The  average  of  nearly  100  determinations  at  the  University 
of  Wisconsin  creamery  during  a  protracted  drought  in  1895 
gave  but  a  trifle  over  8.5  per  cent,  solids  not  fat.  The  casein 
was  low  in  this  milk,  while  the  sugar  was  about  normal  in 
amount.  Similar  conditions  have  been  observed  by  Van  Slyke 
at  the  New  York  station. 

Richmond  states  that  when  the  non-fatty  solids  of  genuine 
whole  milk  are  low,  the  deficiency  is  principally  in  the  milk 
sugar. 

Colostrum. — This  is  the  secretion  in  the  early  stages  of 
lactation,  and  differs  from  ordinary  milk.  It  contains  char- 
acteristic structures,  known  as  colostrum  corpuscles,  and  usually 
contains  much  less  fat  than  fully  developed  milk,  but  a  larger 
proportion  of  proteids.  Colostrum  coagulates  on  boiling. 
Lactose  is  in  small  amount. 
U.  S.  Standard. 

Milk  (whole  milk)  is  the  lacteal  secretion  obtained  by  the 
complete  milking  of  one  or  more  healthy  cows,  properly  fed 
and  kept,  excluding  that  obtained  within  15  days  before  and 


196  FOOD   ANALYSIS 

five  days  after  calving,  and  contains  not  less  than  12  per  cent, 
of  total  solids,  not  less  than  8.5  per  cent,  of  solids  not  fat,  and 
not  less  than  3.25  per  cent,  of  milk  fat. 

Blended  milk  is  milk  modified  in  its  composition  so  as  to 
have  a  definite  and  stated  percentage  of  one  or  more  of  its 
constituents. 

Skim  milk  is  milk  from  which  a  part  or  all  of  the  cream  has 
been  removed  and  contains  not  less  than  9.25  per  cent,  of  milk 
solids. 
Analytic  Processes. 

As  already  noted,  the  specific  gravity  of  milk  rises  gradually 
for  some  time  after  it  has  been  drawn,  and  the  determination 
is  to  be  made  only  after  this  action  has  ceased.  This  will  re- 
quire about  5  hours  after  the  milk  is  drawn,  if  it  has  been 
kept  below  1 5°,  but  at  a  higher  temperature  it  will  be  necessary 
to  allow  at  least  12  hours.  For  all  other  determinations  the 
milk  must  be  analyzed  as  soon  as  possible.  The  following 
figures,  published  by  Bevan,  show  that  a  considerable  loss  in 
total  solids  may  occur  in  24  hours: 

Total  Solids.  Loss. 

Evaporated  immediately, 1 1-73 

Evaporated  after    24  hours, io-79  o-94 

Evaporated  after    48  hours, 10.38  i  .35 

Evaporated  after  120  hours, 9.42  2.31 

The  decomposition  is  very  irregular,  and  it  is  not  possible 
to  determine,  by  estimation  of  the  lactic  acid  or  other  products, 
the  original  composition  of  the  milk.  The  pipet  used  for  taking 
a  portion  for  analysis  should  have  a  wide  opening,  that  no  cream 
may  be  retained  when  the  pipet  is  discharged. 

When  rigid  accuracy  is  not  essential,  it  will  suffice  to  measure 
the  portions  of  milk  taken  for  the  determinations.  -  Vieth  uses 
a  pipet  graduated  to  deliver  5  grams,  and  finds  that,  working 
with  whole  and  skimmed  milk,  under  the  ordinary  variations 
of  temperature,  the  error  will  not  exceed  o.i  on  the  total  solids 
and  is  less  on  the  fat. 


MILK    AND   MILK   PRODUCTS  1 97 

A  good  plan  is  to  use  a  5  c.c.  pipet  and  to  wash  out  that 
which  adheres  to  the  glass  with  a  little  water.  The  specific 
gravity  of  the  milk  being  known,  the  amount  taken  can  be 
calculated.     The  milk  should  be  as  near  15.5°  as  possible. 

Specific  Gravity. — Air-bubbles  are  held  rather  tenaciously 
by  milk,  and  care  must  be  taken  in  mixing,  preparatory  to 
taking  the  specific  gravity,  to  avoid  as  far  as  possible  the 
inclosure  of  the  air,  and  to  allow  sufficient  time  for  the  escape  of 
any  bubbles  that  may  be  present.  The  specific  gravity  of  milk 
is  understood  to  be  taken  at  15.5°;  samples  should  be  brought 
near  to  this.  If  at  a  few  degrees  above  or  below,  it  will  suffice 
to  make  the  determination  at  once  and  obtain  the  correct  figure 
by  reference  to  the  annexed  table.  The  specific  gravity  of 
normal  milk  varies  between  1.028  and  1.035.  The  figure  alone 
does  not  indicate  the  character  of  the  sample,  but  taken  in  con- 
junction with  the  figure  for  fat  or  for  total  solids,  it  is  of  value 
as  a  check  on  the  results  furnished  by  other  determinations. 

The  simplest  method  of  determining  specific  gravity  is  by 
thci  lactodensimeter,  a  delicate  and  accurately  graduated  hydro- 
meter. The  instrument  must  be  immersed  carefully  so  as  not 
to  wet  the  stem  above  the  point  at  which  it  will  rest.  The  in- 
strument should  be  tested  by  immersion  in  distilled  water  at 
15.5°  and  milks  of  known  specific  gravity. 

The  indications  furnished  by  the  lactodensimeter  are  suffi- 
ciently accurate  for  most  purposes,  but  its  employment  neces- 
sitates a  considerable  amount  of  the  sample. 

More  accurate  determination  can  be  made  by  the  methods 
detailed  in  the  introductory  part  (page  3),  the  most  suitable 
being  the  Sprengel  tube.  According  to  Richmond,  the  pyk- 
nometer  is  less  suitable  for  rigidly  accurate  work,  on  account 
of  the  tendency  of  the  cream  to  separate  before  the  mass  has 
acquired  the  standard  temperature. 

Total  Solids. — This  determination  may  often  be  made 
with  sufficient  accuracy  for  practical  purposes  by  evaporating 


igS 


FOOD  ANALYSIS 


a  measured  volume  {e.  ^.,  3  or  5  c.c.)  in  a  shallow  nickel  dish 
from  5  to  8  cm.  in  diameter.  Nickel  crucible-covers  are  suitable. 
The  thin  glass  (Petri)  dishes  used  for  microbe  culture  are  con- 
venient. When  greater  accuracy  is  required,  and  especially 
when  the  ash  is  to  be  determined,  platinum  dishes  must  be 
used.  Satisfactory  results  may  be  secured  by  the  following 
simple  method:  A  flat  platinum  dish,  3.5  cm.  in  diameter, 
with  sides  0.5  cm.  high,  is  provided  with  a  thin  fiat  watch-glass 
cover  that  fits  rather  closely.     The  total  weight  of  the  cover 


Find  the  temperature  of  the  milk  in  one  of  the  horizontal  lines  and  the  specific 
gravity  in  the  first  vertical  column.  In  the  same  line  with  this  and  the  tempera- 
ture the  corrected  specific  gravity  is  given. 


°F. 

50 

51 

52 

53 

54 

55 

56 

57 

58 

59 

60 

61 

62 

Sp. 
Gr. 
21 

20.2 

20.3 

20.3 

20.4 

20.5 

20.6 

20.7 

20.8 

20.9 

20.9 

21.0 

21. 1 

21.2 

22 

21.2 

21.3 

21.3 

21.4 

21.5 

21.6 

21.7 

21.8 

21.9 

21.9 

22.0 

22.1 

22.2 

23 

22.2 

22.3 

22.3 

22.4 

22.5 

22.6 

22.7 

22.8 

22.8  j  22.9 

23.0 

23.1 

23.2 

24 

23.2 

23-3 

23-3 

23-4 

23-5 

23.6 

23.6 

23-7 

23.8 

23-9 

24.0 

24.1 

24.2 

25 

24.1 

24.2 

24.3 

24.4 

24.5 

24.6 

24.6 

24.7 

24.8 

24.9 

25.0 

25-1 

25.2 

26 

25- 1 

25.2 

25.2 

25-3 

25.4 

25.5 

25.6 

25.7 

25.8 

25.9 

26.0 

26.1 

26.2 

27 

26.1 

26.2 

26.2 

26.3 

26.4 

26.5 

26.6 

26.7 

26.8 

26.9 

27.0 

27.1 

27-3 

28 

27.0 

27.1 

27.2 

27-3 

27.4 

27.5 

27.6 

27-7 

27.8 

27.9 

28.0 

28.1 

28.3 

29 

28.0 

28.1 

28.2 

28.3 

28.4 

28.5 

28.6 

28.7 

28.8 

28.9 

29.0 

29.1 

29.3 

30 

29.0 

29.1 

29.1 

29.2 

29.3 

29.4 

29.6 

29.7 

29.8 

29.9 

30.0 

30.1 

30-3 

31 

29.9 

30.0 

30.1 

30.2 

30-3 

30-4 

30-5 

30.6 

30.8 

30-9 

31.0 

31.2 

31.3 

32 

30-9 

31.0 

311 

31.2 

3^-3 

314 

315 

31.6 

31.7 

319 

32.0 

32.2 

32.3 

33 

31.8 

31-9 

32.0 

32.1 

32.3 

32.4 

32.5 

32.6 

32.7 

32.9 

33.0 

33-2 

33-3 

34 

32.7 

32.9 

33.0 

33- 1 

33-2 

33-3 

33-5 

33.6 

33.7 

33.9 

34-c> 

34-2 

34-3 

35 

33-6 

33.8 

33-9 

340 

34-2 

34-3 

34.5 

34.6 

34-7 

34.9 

35-0 

35-2 

35-3 

°C. 

10 

10.5 

II. I 

11.6 

12.2 

12.7 

^3-3 

13.8 

14.4 

15.0 

15-5 

16.1 

16.6 

MILK    AND   MILK   PRODUCTS 


199 


and  dish  is  noted.  2  or  3  c.c.  of  the  sample  are  run  into  the 
dish  from  the  pipet,  the  watch-glass  placed  on,  and  the  weight 
taken  as  rapidly  as  possible.  The  glass  prevents  appreciable 
loss  from  evaporation  during  an  ordinary  weighing.  The  cover 
is  removed,  the  dish  heated  on  the  water-bath  or  in  the  water- 
oven,  and  weighed  from  time  to  time  (with  cover  on  it)  until  the 
weight  is  sensibly  constant.  The  percentage  of  residue  can  be 
easily  calculated.  About  three  hours  may  be  required  to  secure 
constant  weight. 


Find  the  temperature  of  the  milk  in  one  of  the  horizontal  lines  and  the  specific 
gravity  in  the  first  vertical  column.  In  the  same  line  with  this  and  the  tempera- 
ture the  corrected  specific  gravity  is  given. 


63 

64 

65 

66 

67 

68 

69 

70 

71       72 

73       74 

75 

21.3 

21.4 

21-5 

21.6 

21.7 

21.8 

22.0 

22.1 

22.2 

22.3 

22.4 

22.5 

22.6 

22.3 

22.4 

22.5 

22.6 

22.7 

22.8 

23.0 

23.1 

23.2 

233 

23.4 

23.5 

23-7 

23.3 

23.4 

235 

23.6 

237 

23.8 

24.0 

24.1 

24.2 

24.3 

24.4 

24.6 

24.7 

24.3 

24.4 

24-5 

24.6 

24.7 

24.9 

25.0 

25- 1 

25.2 

253 

255 

25.6 

257 

25-3 

254 

25.5 

25.6 

25-7 

25.9 

26.0 

26.1 

26.2. 

26.4 

26.5 

26.6 

26.8 

26.3 

26.5 

26.6 

26.7 

26.8 

27.0:27.1 

27.2 

273 

27.4 

27.5 

27.7 

27.8 

27.4 

27.5 

27.6 

27.7 

27.8 

28.0    28.1 

28.2 

28.3 

28.4 

28.6 

28.7 

28.9 

28.4 

28.5 

28.6 

28.7 

28.8 

1 
29.0  i  29.1 

29.2 

29.4 

295 

29.7 

29.8 

29.9 

29.4 

295 

29.6 

29.8 

29.9 

30.1    30.2 

30-3 

30.4 

30.5 

30.7 

30.9 

31.0 

304 

30.5 

307 

30.8 

30.9 

311    312 

3t.3 

315  1  31.6 

318 

31-9 

32.1 

314 

315 

317 

31.8 

32.0 

32.2    32.2 

32.4 

32.5 

32.6 

32.8 

330 

33'^ 

32.5 

32.6 

32.7 

32:9 

330 

33.2 

33-3 

33-4 

33.6 

33-7 

33-9 

340 

34.2 

33.5 

33.6 

33.8 

33-9 

340 

34.2 

34-3 

34.5 

34.6 

34-7 

34-9 

35-1 

35-2 

34.5 

34.6 

34-8 

34.9 

350 

35.2 

35.3 

35-5 

35.6 

35.8 

36.0 

36.1 

36.3 

35-5 

35-6 

35-8 

35-9 

36.1 

36.2 

36.4 

36.5 

36.7 

36.8 

370 

37-2 

37.3. 

tt: 

~ 

18.3 

18.8 

19.4 

20     20.5 

21. 1 

21.6 

22.2 

22.7 

23-3 

23.8 

200  FOOD    ANALYSIS 

The  A.  O.  A.  C.  method  is:  Heat  at  ioo°  to  constant  weight, 
about  3  grams  in  a  tared  platinum,  aluminum  or  tin  dish  of 
5  cm.  diameter,  with  or  without  the  addition  of  15  to  30  grams 
of  sand.     Cool  and  weigh. 

The  use  of  aluminum  or  tin  as  substitutes  for  platinum  is 
inadvisable,  much  better  results  will  be  obtained  with  nickel, 
porcelain  or  glass. 

Ash. — The  residue  from  the  determination  of  total  solids  is 
heated  cautiously  over  the  Bunsen  burner,  until  a  white  ash 
is  left.  The  result  obtained  in  this  manner  is  apt  to  be  slightly 
low  from  loss  of  sodium  chlorid.  This  may  be  avoided  by 
heating  the  residue  sufficiently  to  char  it,  extracting  the  sol- 
uble matter  with  a  few  cubic  centimeters  of  water,  and  filtering 
(using  paper  extracted  with  hydrofluoric  acid).  The  filter  is 
added  to  the  residue,  the  whole  ashed,  the  filtrate  then  added, 
and  the  liquid  evaporated  carefully  to  dryness.  The  ash  of 
nofmal  milk  is  about  0.7  per  cent,  and  faintly  alkaline.  A 
marked  degree  of  alkalinity  and  effervescence  with  hydro- 
chloric acid  will  suggest  the  addition  of  a  carbonate. 

The  method  of  the  A.  O.  A.  C.  is  as  follows:  In  a  weighed 
dish  put  20  c.c.  of  milk  from  a  weighing  bottle;  add  6  c.c.  of 
nitric  acid,  evaporate  to  dryness,  and  burn  at  a  low  red  heat 
till  the  ash  is  free  from  carbon. 

Fat. — Many  methods  for  fat  determination  have  been  de- 
vised.    The  following  will  suffice  for  all  practical  work: 

Bahcock  Asbestos  Method. — ^This  is  recommended  by  the  A.  O. 
A.  C. :  Provide  a  hollow  cyHnder  of  perforated  sheet  metal  60 
mm.  long  and  20  mm.  in  diameter,  closed  5  mm.  from  one  end 
by  a  disk  of  the  same  material.  The  perforations  should  be 
about  0.7  mm.  in  diameter  and  0.7  mm.  apart.  Fill  the  cylin- 
der loosely  with  from  1.5  to  2.5  grams  of  freshly  ignited  woolly 
asbestos  free  from  fine  or  brittle  material.  Cool  in  a  desiccator 
and  weigh.  Introduce  a  weighed  quantity  of  milk  (about  4 
grams)  and  dry  at  100°.     The  cylinder  is  placed  in  the  ex- 


MILK   AND   MILK   PRODUCTS  20I 

traction  tube  and  extracted  with  ether  in  the  usual  way.  The 
ether  is  evaporated  and  thb  fat  weighed.  The  extracted  cyl- 
inder may  be  dried  at  ioo°  and  the  fat  checked  by  the  loss  in 
weight.  A  higher  degree  of  accuracy  is  secured  by  performing 
the  drying  operation  in  hydrogen. 

Adams'  Method. — This  consists  essentially  in  spreading  the 
milk  over  absorbent  paper,  drying,  and  extracting  the  fat  in  an 
extraction  apparatus;  the  milk  is  distributed  in  an  extremely 
thin  layer,  and  by  a  selective  action  of  the  paper  the  larger 
portion  of  the  fat  is  left  on  the  surface.  A  paper,  manufac- 
tured especially  for  this  purpose  by  Schleicher  &  Schuell,  is 
obtainable  in  strips  of  suitable  size.  Each  of  these  yields  to 
ether  only  from  o.ooi  to  0.002  gram  of  extract. 

Coils  made  of  thick  filter-paper,  cut  into  strips  6  by  62  cm., 
are  thoroughly  extracted  with  ether  and  alcohol,  or  the  weight 
of  the  extract  corrected  by  a  constant  obtained  for  the  paper. 
From  a  weighing  bottle  about  5  grams  of  the .  milk  are  trans- 
ferred to  the  coil  by  means  of  a  pipet,  care  being  taken  to 
keep  dry  the  end  of  the  coil  held  in  the  fingers.  The  coil  is 
placed,  dry  end  down,  on  a  piece  of  glass  and  dried  for  one  hour, 
preferably  in  an  atmosphere  of  hydrogen;  it  is  then  transferred 
to  an  extraction  apparatus  and  extracted  with  absolute  ether, 
petroleum  spirit  of  boiling-point  about  45°  or,  better,  carbon 
tetrachlorid.     The  extracted  fat  is  dried  and  weighed. 

The  above  procedure  is  very  satisfactory,  but  the  drying 
in  hydrogen  may  usually  be  omitted.  After  the  coil  has  re- 
ceived at  least  twenty  washings,  the  flask  is  detached,  the  ether 
removed  by  distillation,  and  the  fat  dried  by  heating  in  an  air- 
oven  at  about  105°,  and  occasionally  blowing  air  through  the 
flask.  After  cooling,  the  flask  is  wiped  with  a  piece  of  silk, 
allowed  to  stand  ten  minutes,  and  weighed. 

Richmond  states  that  to  perform  a  rigidly  accurate  deter- 
mination attention  to  the  following  points  is  necessary:  The 
ether  must  be  anhydrous   (drying  over  calcium  chlorid  and 


202 


FOOD   ANALYSIS 


distilling  is  sufficient).  Schleicher  &  Schuell's  fat-free  papers 
should  be  used,  and  one  should  be  extracted  without  any  milk 
on  it,  as  a  tare  for  the  others.  Four  or  five  hours'  extraction 
is  necessary,  and  the  coils  should  be  well  dried  before  extraction 
is  begun. 

Thimble- shaped  cases  made  of  fat-free  paper  are  now  ob- 
tainable and  are  convenient  for  holding  the  absorbent  material 
on  which  the  milk  is  spread.  The  fine  texture  prevents  un- 
dissolved matter  escaping.  A  case  may 
be  used  repeatedly.  Sour  milk  may  be 
thinned  with  ammonium  hydroxid  before 
taking  the  portion  for  analysis. 

Werner- Schmid  Method. — This  is  suita- 
ble for  sour  milk  and  for  sweetened  con- 
densed milk.  I  oc.c.  of  the  milk  are  meas- 
ured into  a  long  test-  tube  of  50  c.c.  capac- 
ity, and  10  c.c.  of  strong  hydrochloric  acid 
added,  or  the  milk  may  be  weighed  in  a 
small  beaker  and  washed  into  the  tube 
with  the  acid.  After  mixing,  the  liquid 
is  boiled  ij  minutes,  or  the  tube  may  be 
corked  and  heated  in  the  water-bath  from 
5  to  10  minutes,  until  the  liquid  turns 
dark  brown.  It  must  not  be  allowed  to 
turn  black.  The  tube  and  contents  are 
cooled  in  water,  30  c.c.  of  well-washed  ether  added,  shaken, 
and  allowed  to  stand  until  the  line  of  acid  and  ether  is 
distinct.  The  cork  is  taken  out,  and  a  double-tube  arrange- 
ment, like  that  of  the  ordinary  wash-bottle,  inserted.  The 
stopper  of  this  should  be  of  cork  and  not  of  rubber,  since 
it  is  difficult  to  slide  the  glass  tube  in  rubber,  and  there  is  a  pos- 
sibility, also,  of  the  ether  acting  on  the  rubber  and  dissolving  it. 
The  lower  end  of  the  exit-tube  is  adjusted  so  as  to  rest  im- 
mediately above  the  junction  of  the  two  liquids.     The  ethereal 


Fig. 


45- 


MILK  AND   MILK  PRODUCTS  203 

solution  of  the  fat  is  then  blown  out  and  received  in  a  weighed 
flask.  Two  more  portions  of  ether,  10  c.c.  each,  are  shaken 
with  the  acid  liquid,  blown  out,  and  added  to  the  first.  The 
ether  is  then  distilled  off  and  the  fat  dried  and  weighed  as  above. 

Centrijugal  Methods. — Among  the  processes  for  the  rapid 
determination  of  fat,  those  employing  centrifugal  action  have 
been  found  most  convenient.  The  following  method,  devised 
by  Leffmann  &  Beam  in  1889,^^  has  proved  satisfactory  on 
the  score  of  accuracy,  simplicity,  and  ease  of  manipulation. 
This  process,  which  antedates  in  its  successful  operation 
and  public  exhibition  all  the  rapid  centrifugal  methods  except 
the  De  Laval,  is  sometimes  called  the  "Beimling"  method, 
but  Beimling  was  merely  a  patentee  of  a  crude  form  of  cen- 
trifugal machine,  and  had  no  part  in  devising  the  mixture  for 
freeing  the  fat.  The  distinctive  feature  is  the  use  of  fusel  oil, 
the  effect  of  which  is  to  produce  a  greater  difference  in  surface 
tension  between  the  fat  and  the  liquid  in  which  it  is  suspended, 
and  thus  promote  its  readier  separation.  This  effect  has  been 
found  to  be  heightened  by  the  presence  of  a  small  amount  of 
hydrochloric  acid. 

The  test-bottles  have  a  capacity  of  about  30  c.c.  and  are 
provided  with  a  graduated  neck,  each  division  of  which  repre- 
sents 0.1  per  cent,  by  weight  of  butter  fat. 

15  c.c.  of  the  milk  are  measured  into  the  bottle,  3  c.c.  of  a 
mixture  of  equal  parts  of  amyl  alcohol  and  strong  hydro- 
chloric acid  added,  mixed,  the  bottle  filled  nearly  to  the  neck 
with  concentrated  sulfuric  acid,  and  the  liquids  mixed  by 
holding  the  bottle  by  the  neck  and  giving  it  a  gyratory  mo- 
tion. The  neck  is  now  filled  to  about  the  zero  point  with  a 
mixture  of  sulfuric  acid  and  water  prepared  at  the  time.  It 
is  then  placed  in  the  centrifugal  machine,  which  is  so  arranged 
that  when  at  rest  the  bottles  are  in  a  vertical  position.  If  only 
one  test  is  to  be  made,  the  equilibrium  of  the  machine  is  main- 
tained by  means  of  a  test-bottle,  or  bottles,  filled  with  a  mixture 


204  FOOD   ANALYSIS 

of  equal  parts  of  sulfuric  acid  and  water.  After  rotation  for 
from  one  to  two  minutes,  the  fat  will  collect  in  the  neck  of  the 
bottle  and  the  percentage  may  be  read  off.  It  is  convenient  to 
use  a  pair  of  dividers  in  making  the  reading.  The  legs  of  these 
are  placed  at  the  upper  and  lower  limits  respectively  of  the  fat, 
allowance  being  made  for  the  meniscus;  one  leg  is  then  placed 
at  the  zero  point  and  the  reading  made  with  the  other.  Ex- 
perience by  analysts  in  various  parts  of  the  world  has  shown 
that  with  properly  graduated  bottles  the  results  are  reliable. 
As  a  rule,  they  do  not  differ  more  than  o.i  per  cent,  from  those 
obtained  by  the  Adams  process,  and  are  generally  even  closer. 

For  great  accuracy,  the  factor  for  correcting  the  reading  on 
each  of  the  bottles  should -be  determined  by  comparison  with 
the  figures  obtained  by  the  Adams  or  other  standard  process. 

Cream  is  to  be  diluted  to  exactly  ten  times  its  volume,  the 
specific  gravity  taken,  and  the  liquid  treated  as  a  milk.  Since 
in  the  graduation  of  the  test-bottles  a  specific  gravity  of  1.030 
is  assumed,  the  reading  must  be  increased  in  proportion. 

A  more  accurate  result  may  be  obtained  by  weighing  in  the 
test-bottle  about  2  c.c.  of  the  cream  and  diluting  to  about  15  c.c. 
The  reading  obtained  is  to  be  multiplied  by  15.45  and  divided 
by  the  weight  in  grams  of  cream  taken. 

The  mixture  of  fusel  oil  and  hydrochloric  acid  seems  to  be- 
come less  satisfactory  when  long  kept.  It  should  be  clear  and 
not  very  dark  in  color.  It  is  best  kept  in  a  bottle  provided  with 
a  pipet  which  can  be  filled  to  the  mark  by  dipping.  Rigid 
accuracy  in  the  measurement  is  not  needed. 

See  also  Cochran's  method  under  "Condensed  Milk." 

Calculation  Methods. — Several  investigators  have  proposed 
formulae  by  which  when  any  two  of  the  data,  specific  gravity, 
fat,  and  total  solids,  are  known,  the  third  can  be  calculated. 
These  vary  according  to  the  method  of  analysis  employed. 
That  of  Hehner  and  Richmond,  as  corrected  by  Richmond, 
was  deduced  from  results  by  the  Adams  method  of  fat  extrac- 


MILK  AND   MILK  PRODUCTS  205 

tion,  and  has  been  found  to  be  the  most  satisfactor>\  It  is  as 
follows: 

T  =  o.25  G  +  1.2  F  +  0.14; 

in  which  T  is  the  total  soHds,  G  the  last  two  figures  of  the  specific 
gravity  (water  being  looo),  and  P  the  fat.  A  table  based  upon 
this  formula  is  annexed. 

A  formula  has  been  devised  by  Richmond  by  which  the  lac- 
tose and  proteids  may  be  calculated  (approximately),  the  specific 
gravity,  fat,  total  soUds,  and  ash  being  known.    Thus: 

G 


P  =  2.8T  +  2.5A  — 3.33  F  — 0.7 


D 


in  which  P  is  the  proteids,  T  the  total  solids,  A  the  ash,  F  the 
fat,  D  specific  gravity  (water  at  15.5°  being  taken  as  i),  and 
G  1000  D  —  1000. 

The  difference  between  the  total  solids  and  the  fat,  proteids, 
and  ash  gives  the  lactose.  In  this  formula  it  has  been  assumed 
that  everything  that  is  not  fat,  proteids,  or  ash,  is  milk-sugar, 
an  assumption  which  is  not  strictly  correct,  and  which  intro- 
duces a  small  error.  Another  slight  error  is  introduced  by  the 
fact  that  the  ash  in  milk  is  not  the  same  as  the  salts  existing 
in  the  milk. 

Total  Proteids. — For  practical  purposes  the  total  pro- 
teids are  best  estimated  by  calculation  from  the  total  nitrogen 
obtained  by  the  Kjeldahl-Gunning  method.  Milk  contains, 
however,  a  sensible  proportion  of  non-proteid  nitrogen.  Ac- 
cording to  Munk,  this  may  range,  in  cows'  milk,  from  0.022 
to  0.034  per  cent.,  and  from  0.014  to  0.026  per  cent,  in  human 
milk.  By  these  figures,  the  average  proteid  nitrogen  in  cows' 
milk  would  be  94  per  cent.,  and  in  human  milk  91  per  cent., 
of  the  total  nitrogen. 

The  determination  of  total  nitrogen  as  recommended  by  the 
A. O. A. C.  is  to  place  in  the  digestion  flask  a  known  weight  (about 
5  grams)  of  the  sample  and  proceed,  without  evaporation,  as 


206 


FOOD  ANALYSIS 


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2 

MILK  AND  MILK   PRODUCTS  207 

described  on  page  ;^^.  The  best  factor  for  converting  nitrogen 
to  proteids  is  6.38. 

Ritihausen  Method. — This  method  depends  on  precipitation 
by  copper  sulfate  and  sodium  hydroxid.  It  is  applicable  only 
to  fully  developed  milks;  the  proteids  of  colostrum  and  whey 
are  only  partially  precipitated.  The  reagents  are  given  on 
page  113. 

10  grams  of  milk  are  placed  in  a  beaker,  diluted  with  100 
c.c.  of  distilled  water,  5  c.c.  of  copper  sulfate  solution  added, 
and  thoroughly  mixed.  The  sodium  hydroxid  solution  is  then 
added  drop  by  drop,  with  constant  stirring,  until  the  precipitate 
settles  quickly  and  the  liquid  is  neutral,  or  at  most  very  feebly 
acid.  An  excess  of  alkali  will  prevent  the  precipitation  of  some 
of  the  proteids. 

The  reaction  should  be  tested  on  a  drop  of  the  clear  liquid, 
withdrawing  it  by  means  of  a  rod,  taking  care  not  to  include 
any  solid  particles.  When  the  operation  is  correctly  performed, 
the  precipitate,  which  includes  the  fat,  settles  quickly,  and  car- 
ries down  all  of  the  copper.  It  is  washed  by  decantation  with 
about  100  c.c.  of  water,  and  colleced  on  a  filter  (previously  dried 
at  130°  and  weighed  in  a  weighing  bottle).  The  portions  ad- 
hering to  the  sides  of  the  beaker  are  dislodged  with  the  aid  of  a 
rubber-tipped  rod.  The  contents  of  the  filter  are  washed  with 
water  until  250  c.c.  are  collected,  which  are  mixed  and  reserved 
for  the  determination  of  the  sugar  as  described  below.  The 
water  in  the  precipitate  is  removed  by  washing  once  with  strong 
alcohol,  and  the  fat  by  six  or  eight  washings  with  ether.  An 
extraction  apparatus  may  be  used  for  this  purpose.  The  wash- 
ings being  received  in  a  weighed  flask,  the  determination  of 
the  fat  may  be  made  by  evaporating  the  ether,  with  the  usual 
precautions. 

The  residue  on  the  filter,  which  consists  of  the  proteids  in 
association  with  copper  hydroxid,  is  washed  with  absolute 
alcohol,  which  renders  it  more  granular,  and  then  dried  at  130° 


2o8  FOOD    ANALYSIS 

in  the  air-bath.  It  is  weighed  in  a  weighing  bottle,  transferred  to 
a  porcelain  crucible,  incinerated,  and  the  residue  again  weighed. 
The  weight  of  the  filter  and  contents,  less  that  of  the  filter 
and  residue  after  ignition,  gives  the  weight  of  the  proteids. 
The  results  by  this  method  are  slightly  high,  since  copper  hy- 
droxid  does  not  become  completely  converted  into  copper  oxid 
at  130.° 

Richmond  &  Boseley  have  modified  the  process  by  diluting 
the  milk  to  200  c.c,  adding  a  httle  phenophthalein,  and  neu- 
tralizing any  acidity  by  the  cautious  addition  of  dilute  sodium 
hydroxid  solution,  then  adding  from  2.0  to  2.5  c.c.  of  the  copper 
sulfate  solution.  The  precipitate  is  allowed  to  settle,  washed, 
and  estimated  as  above. 

Casein  and  Albumin. — The  most  accurate  separation  of 
casein  and  albumin  is  made  by  Sebelein's  method,  as  follows: 
20  c.c.  of  the  sample  are  mixed  with  40  c.c.  of  a  saturated  solu- 
tion of  magnesium  sulfate  and  powdered  magnesium  sulfate 
stirred  in  until  no  more  will  dissolve.  The  precipitate  of  casein 
and  fat,  including  the  trace  of  globulin,  is  allowed  to  settle,  fil- 
tered, and  washed  several  times  with  a  saturated  solution  ^f 
magnesium  sulfate.  The  filtrate  and  washings  are  saved  for 
the  determination  of  albumin.  The  filter  and  contents  are 
transferred  to  a  flask  and  the  nitrogen  determined  by  the 
method  described  above.  The  nitrogen  so  found,  multiplied 
by  6.38,  gives  the  casein. 

The  filtrate  and  washings  from  the  determination  of  casein 
are  mixed,  the  albumin  precipitated  by  Almen's  tannin  reagent, 
filtered,  and  the  nitrogen  in  the  precipitate  determined  as  above. 
The  same  factor  is  used. 

Almen's  reagent  is  prepared  by  dissolving  4  grams  of  tan- 
nin in  190  c.c.  of  50  per  cent,  alcohol  and  adding  8  c.c.  of  acetic 
acid  of  25  per  cent. 

In  a  mixture  of  milk  and  whey  (prepared  with  rennet)  in 
about  equal  parts,  Richmond  and   Boseley  found  about  0.3 


MILK  AND  MILK   PRODUCTS  209 

per  cent,  of  albumoses  not  precipitated  by  the  copper  sulfate 
nor  by  magnesium  sulfate,  but  precipitable,  along  with  the 
albumin,  by  a  solution  of  tannin.  The  separation  may  be 
effected  by  diluting  the  filtrate  from  the  magnesium  sulfate  pre- 
cipitation, acidifying  slightly  with  acetic  acid,  and  boiling, 
when  the  albumin  will  be  coagulated  and  precipitated.  The 
albumoses  may  be  separated  by  filtering  the  solution  and  pre- 
cipitating with  tannin  solution.  The  precipitated  proteids  are 
best  estimated  by  determining  the  nitrogen  in  the  moist  preci- 
pitate. The  separation  of  the  proteids  may  be  effected,  though 
less  accurately,  by  the  use  of  acetic  acid,  as  recommended  by 
Hoppe-Seyler  and  Ritthausen. 

The  following  are  A.  O.  A.  C.  methods: 

1.  Provisional  Method  jor  the  Determination  oj  Casein  in 
Cows^  Milk. — The  determination  should  be  made  when  the 
milk  is  fresh.  When  it  is  not  practicable  to  make  the  deter- 
mination within  24  hours,  add  one  part  of  formaldehyde  to 
2500  parts  of  milk  and  keep  in  a  cool  place.  10  grams  of  the 
sample  are  diluted  with  about  90  c.c.  of  water  at  between  40° 
and  42°,  1.5  c.c.  of  a  solution  containing  10  per  cent,  of  acetic 
acid  by  weight  added,  allowed  to  stand  for  five  minutes, 
washed  three  times  by  decantation,  pouring  the  washings 
through  a  filter,  and  the  precipitate  transferred  completely  to 
the  filter.  If  the  filtrate  is  not  clear  at  first,  it  will  generally 
become  so  in  two  or  three  filtrations,  after  which  the  washing 
can  be  completed.  The  nitrogen  in  the  washed  precipitate 
and  filter  is  determined  by  the  Kjeldahl- Gunning  method. 
The  nitrogen,  multiplied  by  6.38,  gives  the  casein. 

In  working  with  milk  which  has  been  kept  with  preservatives, 
the  acetic  acid  should  be  added  in  small  portions,  a  few  drops 
at  a  time  with  stirring,  and  the  addition  continued  until  the 
liquid  above  the  precipitate  becomes  clear  or  nearly  so. 

2.  Provisional  Method  jor  the  Determination  oj  Albumin  in 
Milk. — The  filtrate  obtained  in  the  above  operation  is  neutral- 

or  THE 

UNIVERSITY 


2IO  FOOD   ANALYSIS 

ized  with  sodium  hydroxid,  0.3  c.c.  of  the  10  per  cent,  solution  of 
acetic  acid  added,  and  the  mixture  heated  for  15  minutes. 
The  precipitate  is  collected  on  a  filter,  washed,  and  the  nitro- 
gen determined. 

We  have  found  the  following  method  satisfactory,  avoiding 
the  difficulty  of  washing  the  precipitate:  10  c.c.  of  the  milk 
are  mixed  with  saturated  magnesium  sulfate  solution  and  the 
powdered  salt  added  to  saturation.  The  mixture  is  washed 
into  a  graduated  measure  with  a  small  amount  of  the  saturated 
solution,  made  up  to  100  c.c.  with  the  same  solution,  mixed, 
and  allowed  to  stand  until  the  separation  takes  place.  As 
much  as  possible  of  the  clear  portion  is  drawn  off  with  a  pipet 
and  passed  through  a  dry  filter.  An  aliquot  portion  of  the 
filtrate  is  taken,  the  albumin  precipitated  by  a  solution  of  tan- 
nin, and  the  nitrogen  in  the  precipitate  determined  as  above. 

The  casein  is  found  by  subtracting  the  figure  for  albumin 
from  that  for  total  proteids. 

Lactose. — Soxhlet's  method,  adopted  by  the  A.  O.  A.  C,  is 
as  follows:  25  c.c.  of  the  sample  in  a  500  c.c.  flask  are  diluted 
with  400  c.c.  of  water  and  10  c.c.  of  copper  sulfate  solution 
(34.639  grams  crystallized  copper  sulfate  in  500  c.c.)  and  8.8 
c.c.  -^  sodium  hydroxid  solution  added.  (The  mixture  should 
still  have  an  acid  reaction  and  contain  copper  in  solution.  If 
this  is  not  the  case,  the  experiment  must  be  repeated,  using  a 
little  less  of  the  alkah.)  The  flask  is  filled  to  the  mark  with 
water,  shaken,  and  the  liquid  passed  through  a  dry  filter.  50 
c.c.  of  the  mixed  copper  reagent  (page  113)  are  heated  to 
brisk  boiling  in  a  300  c.c.  beaker,  100  c.c.  of  the  filtrate  obtained 
as  above  added,  and  boiling  continued  for  six  minutes;  the 
liquid  then  promptly  filtered,  and  treated  according  to  methods 
given  on  pages  114  to  117.  The  amount  of  lactose  is  calculated 
by  the  table  on  page  211  from  the  copper  obtained  by  table. 
The  figures  for  weights  of  copper  between  any  two  data  given 
in  the  table  may  be  calculated  with  sufficient  accuracy  for 


MILK  AND  MILK  PRODUCTS 


211 


practical  purposes  by  allowing  0.0008  gram  of  lactose  for  each 
o.ooi  gram  of  copper. 


Copper. 

Lactose. 

Copper. 

Lactose. 

Copper. 

Lactose. 

O.IOO 

0.072 

0.205 

0.151 

0305 

0.228 

0.105 

0.075 

0.210 

0.154 

0.310 

0.232 

0.1 10 

0.079 

0.215 

0.158 

0-315 

0.236 

0.I15 

0.083 

0.220 

0.162 

0.320 

0.240 

0.120 

0086 

0.225 

0.165 

0.325 

0.244 

0.125 

0.090 

0.230 

0.169 

0.330 

0.248 

0.130 

0.094 

0.235 

0.173 

0.335 

0.252 

0.135 

0.097 

0.240 

0.177 

0.340 

0.256 

0.140 

O.IOI 

0.245 

0.181 

0.345 

0.260 

0.145 

0.105 

0.250 

0.185 

0.350 

0.264 

0.150 

0.109 

0.255 

0.189 

0.355 

0.268 

0155 

0.1 12 

0.260 

0.192 

0.360 

0.272 

0.160 

0.116 

0.265 

0.196 

0.365 

0.276 

0.165 

0.120 

0.270 

0.200 

0.370 

0.280 

0.170 

0.124 

0.275 

0.204 

0.375 

0.285 

0-I75 

0.128 

0.280 

0.208 

0.380 

0.289 

0.180 

0.132 

0.285 

0.212 

0.385 

0.293 

0.185 

0.134 

0.290 

0.216 

0.390 

0.298 

0.190 

0.139 

0.295 

0.221 

0.395 

0.302 

0.195 

0.141 

0.300 

0.224 

0.400 

0.306 

0.200 

0.147 

Lactose  may  be  determined  by  the  polarimeter  after  removal 
of  the  fat  and  proteids,  which  is  best  effected,  as  recommended 
by  Wiley,  by  a  mercuric  nitrate  solution,  prepared  by  dissolving 
mercury  in  twice  its  weight  of  nitric  acid  of  1.42  sp.  gr.  and  add- 
ing to  the  solution  five  volumes  of  water.  The  A.  O.  A.  C. 
optical  method  is  as  follows : 

For  polarimeters  reading  to  100  for  26.048  grams  sucrose 
(corresponding  to  32.98  grams  lactose),  measure,  in  c.c,  the 
amount  obtained  by  dividing  double  this  {i.  e.,  65.96)  by  the 
specific  gravity,  add  10  c.c.  mercuric  nitrate  solution,  make  up 
to  102.6  c.c,  shake,  filter  through  a  dry  filter  and  examine  in  a 
200  mm.  tube.     Half  the  observed  reading  will  be  the  per- 


212  FOOD   ANALYSIS 

centage  of  lactose.  For  example,  if  the  specific  gravity  of  the 
milk  is  1.030,  the  amount  taken  will  be  65.96  -^  1.030=64  c.c. 

The  allowance  for  volume  of  precipitate  by  making  up  to 
102.6  c.c.  is  not  accurate,  except  with  closely- skimmed  milks. 

The  correction  may  be  made  more  closely  by  calculating 
the  actual  volume  of  the  precipitate  by  multiplying  the  fat-per- 
centage by  1.075  (average  specific  volume  of  fat)  and  the 
proteid-percentage  by  0.8  (average  specific  volume  of  coagulated 
proteids),  deducting  the  sum  of  these  products  from  100  c.c. 
and  correcting  the  observed  reading  by  proportion.  For 
ordinary  milk,  the  volume  of  the  proteids  from  65.96  grams  may 
be  taken  at  1.68  c.c.  Supposing  the  sample  to  contain  4.0  per 
cent,  of  fat  and  the  polarimetric  reading  to  be  10,  the  calcula- 
tion would  be  thus: 

65.96  X  0.04     =  2.63  Amount  of  fat  in  milk  taken 

2.63  X  I -075  =  2.82  c.c.  Volume  of  fat  in  precipitate 

1.68  c  c.  Est.  vol.  of  proteids  in  precipitate 

4.50  c.c.  Total  volume  of  precipitate 
100    —   4.50  =  95.5    c.c.  Actual  volume  of  liquid. 
100:  95.5::  10   :   9.55  9.55  -^  2  =  4.75,  percent,  lactose 

The  employment  of  a  factor  for  correcting  for  the  volume  of 
precipitate  may  be  avoided  by  Scheibler's  method  of  ''double 
dilution"  (see  page  21),  in  which  two  solutions  of  different  vol- 
ume are  compared.  The  following  is  a  summary  of  the  method 
given  by  Wiley  &  Ewell:  For  polarimeters  adapted  to  a  normal 
weight  of  26.048  sucrose,  65.82  grams  of  milk  are  placed  in 
a  100  c.c.  flask,  10  c.c.  of  the  acid  mercuric  nitrate  added,  the 
flask  filled  to  the  mark,  the  contents  well  mixed,  filtered,  and 
a  reading  taken.  A  similar  quantity  of  the  milk  is  placed 
in  a  200  c.c.  flask  and  treated  in  the  same  way.  The  true 
reading  is  obtained  by  dividing  the  product  of  the  two  readings 
by  their  difference.  If  the  observations  are  made  in  a  200  mm. 
tube  the  percentage  is  half  the  true  reading. 

The  instrument  should  be  accurate,  and  great  care  taken  in 


MILK  AND   MILK   PRODUCTS  213 

the  work,  or  the  results  will  be  less  satisfactory  than  by  the 
method  first  described,  in  which  an  allowance  is  made  for  the 
volume  of  the  precipitate. 

Birotation. — When  freshly  dissolved  in  cold  w^ater,  lac- 
tose shows  a  higher  rotation  than  that  given  above.  By  stand- 
ing, or  immediately  on  boiling,  the  rotatory  power  falls  to  the 
point  mentioned.  In  preparing  solutions  from  the  solid,  there- 
fore, care  must  be  taken  to  bring  them  to  the  boiling- 
point  previous  to  making  up  to  a  definite  volume.  This  precau- 
tion is  unnecessary  when  operating  on  milk. 

Adulterations. — The  addition  of  water  to  milk  is  usually 
detected  by  the  diminution  in  the  amount  of  solids.  The  ad- 
dition of  water  decreases  the  specfic  gravity,  while  abstraction 
of  fat  increases  it. 

Several  observers  have  found  that  the  whey  (milk-serum) 
obtained  by  a  routine  method  is  of  constant  composition  and 
that  by  its  specific  gravity  or  refractive  index,  watering  may  be 
detected.  Woodman^^  recommends  the  following  method  for 
obtaining  a  standard  whey:  loo  c.c.  of  the  sample  are  mixed 
with  2  c.c.  of  dilute  acetic  acid  (sp.  gr.  1035,  containing  25  per 
cent,  acetic  acid),  the  vessel  covered  with  a  watch-glass  and  heated 
in  the  water-bath  for  20  minutes,  at  70.°  It  is  then  placed 
in  ice- water  for  10  minutes,  and  the  solution  filtered.  The 
specific  gravity  may  be  taken  under  the  usual  precautions,  or? 
as  suggested  by  Leach,^^  the  refractive  index  may  be  observed. 
The  routine  of  precipitation  must  be  closely  followed,  as  the 
amount  of  proteids  precipitated  differs  with  the  method.  The 
total  solids  and  polarimetric  reading  of  the  whey  might  be  taken 
as  additional  data.  The  latter  figure  will  be  somewhat  less 
than  that  due  to  the  milk-sugar,  as  the  proteids  in  solution  are 
levorotatory. 

The  following  are  some  of  the  limits  recorded,  but  analysts 
should  make  determinations  on  samples  of  known  composition. 

For  the  Zeiss  immersion  refractometer,  an  instrument  of 
special  construction,  Leach   &    Lythgoe***  consider  39  as  the 


214  FOOD   ANALYSIS 

lowest  permissible  reading.  This  corresponds  to  1.3424  on  the 
Abbe  refractometer. 

From  unwatered  whole  milk,  Leach  obtained  a  serum  of  sp. 
gr.  1.0287;  from  unwatered  centrifugal  skimmed  milk,  a  serum 
of  1.0296,  at  15°. 

Vieth  has  pointed  out  that  in  normal  milks  the  ratio  sugar: 
proteids  :  ash  =13:9:2  exists,  and  a  determination  of  these 
ratios  may  aid  in  the  attempt  to  distinguish  genuine  but  ab- 
normal milks  from  watered  milks.  In  the  case  of  a  watered 
milk  the  proportion  would  remain  unchanged,  but  in  abnormal 
milk  it  has  been  found  to  vary. 

Richmond  states  that  the  determination  of  the  amount  of 
water  that  has  been  added  to  milk  is  best  calculated  from  the 
figures  obtained  by  adding  the  difference  between  the  specific 
gravity  of  the  sample  and  1000  to  the  figure  representing  the 
percentage  of  the  fat.  Thus,  if  a  milk  have  the  specific  gravity 
of  1029.2  and  contain  3.27  per  cent,  of  fat,  the  figure  from  which 
the  water  is  calculated  is29.2  +  3.27===32.47.  The  mean  figure 
from  unadulterated  milks  was  found  to  be  36.0,  but  34.5  is  con- 
sidered to  be  a  safer  limit.  Accepting  this  figure,  the  percen- 
tage of  added  water  in  the  sample  given  above  will  be  found  by 
the  proportion  34.5  :  23.47  :  100  ::  94.1,  i.  e.,  the  sample  contains 
5.9  per  cent,  of  water.  Experiments  on  milks  which  had  been 
diluted  with  known  proportions  of  water  showed  that  this  method 
of  calculating  the  added  water  gave  nearer  approximations  to 
the  truth  than  by  calculating  from  the  figure  for  non- fatty  solids. 

It  is  stated  that  the  watering  of  milk  can  be  detected  by  the 
lowering  of  the  freezing-point.  The  freezing-point  of  whole 
milk  ranges  from  — 0.55  to  — 0.57.  Bomstein*^  claims  that  as 
little  as  5  per  cent,  added  water  can  be  detected  by  this  method. 
The  special  apparatus  devised  for  these  determinations  (known 
as  "cryoscopy")  must  be  used,  and  the  data  must  be  determined 
by  each  observer  in  order  to  be  safely  comparable. 

For  ordinary  milk  control  it  will  suffice  to  take  the  specific 


MILK   AND   MILK   PRODUCTS  215 

gravity  by  the  lactodensimeter  (see  page  107)  and  the  fat  by  the 
Leffmann-Beam  method.  From  the  figures  thus  obtained  the 
total  solids  can  be  ascertained  from  the  table  or  Richmond's 
slide-rule. 

Coloring  and  Thickening  Agents. — Several  instances  of  the 
use  of  brain-matter,  dextrin,  and  gelatin  have  been  recorded. 
It  is  also  stated  that  sugar,  salt,  and  starch  have  been  added. 
Thickening  agents  of  pectinous  nature  are  now  commercial 
articles.  For  some  information  concerning  them  see  under 
''Agar."  A  solution  of  10.5  per  cent,  sugar  and  5.5  per  cent, 
calcium  oxid  has  been  sold  under  the  name  "Grossin"  for 
thickening  cream.  It  could,  of  course,  be  at  once  detected  by 
the  increased  polarimetric  reading  and  increased  ash.  Starch 
will  be  easily  detected  by  the  iodin  test.  Coloring  matters  are 
used  to  conceal  inferiority  in  quality. 

At  the  present  time  preparations  of  annatto,  turmeric,  and 
some  coal-tar  colors  are  used,  especially  the  latter.  Caramel 
is  occasionally  used,  saffron  and  carotin  but  rarely.  Annatto 
may  be  detected  by  rendering  the  sample  slightly  alkaline  by 
acid  sodium  carbonate,  immersing  a  slip  of  filter-paper,  and 
allowing  it  to  remain  overnight.  Annatto  will  cause  a  reddish- 
yellow  stain  on  the  paper. 

Leys  gives  the  following  method  for  detecting  annatto: 
50  c.c.  of  the  sample  are  shaken  with  40  c.c.  of  95  per  cent, 
alcohol,  50  c.c.  of  ether,  3  c.c.  of  water,  and  1.5  c.c.  of  am- 
monium hydroxid  solution  (sp.  gr.  0.900),  and  allowed  to  stand 
for  20  minutes.  The  lower  layer,  which  in  presence  of  annatto 
will  have  a  greenish-yellow  tint,  is  tapped  off  and  gradually 
treated  with  half  its  measure  of  10  per  cent,  solution  of  sodium 
sulfate,  the  separator  being  inverted  without  shaking,  •  after 
each  addition.  By  this  treatment  the  casein  separates  in  flakes 
which  conglomerate  and  rise  to  the  surface,  when  the  adjacent 
liquid  is  tapped  off,  strained  through  wire  gauze,  and  placed  in 
four  test-tubes.     To  each  of  these  amyl  alcohol  is  added,  and 


2l6  FOOD   ANALYSIS 

the  tubes  shaken  and  immersed  in  cold  water,  which  is  gradually 
raised  to  80°.  This  causes  the  emulsion  to  break  up,  and  the 
alcohol,  holding  the  annatto  in  solution,  to  come  to  the  surface. 
The  alcoholic  layer  is  separated  from  the  lower  stratum,  evapo- 
rated to  dryness,  and  the  residue  dissolved  in  warm  water  con- 
taining a  little  alcohol  and  ammonium  hydroxid.  A  bundle  of 
white  cotton  fibers  is  introduced  and  the  liquid  evaporated 
nearly  to  dryness  on  the  water-bath.  The  fiber,  which  is  colored 
a  pale  yellow,  even  with  pure  milk,  is  washed  and  immersed 
in  a  solution  of  citric  acid,  when  it  will  be  immediately  colored 
rose-red  if  the  milk  contained  annatto.  Saffron,  turmeric,  and 
the  coloring-matter  of  marigolds  do  not  give  a  similar  reaction. 

Coal-tar  colors  may  often  be  detected  by  the  wool-test  (p. 
64),  but  Lythgoe  has  devised  the  following  method,  which  he 
finds  very  satisfactory:  15  c.c.  of  the  sample  are  mixed  in  a 
porcelain  basin  with  an  equal  volume  of  hydrochloric  acid  (sp. 
gr.  1.20),  and  the  mass  shaken  gently  so  as  to  break  the  curd 
into  coarse  lumps.  If  the  milk  contains  an  azo-color,  the  curd 
will  be  pink ;  with  normal  milk  the  curd  will  be  white  or  yellow- 
ish.    (See  next  page;  also  under ''Butter.") 

Salt  and  cane-sugar  are  occasionally  added  to  milk  that  has 
been  diluted  with  water.  The  former  is  detected  by  the  taste, 
the  increased  proportion  of  ash  and  of  chlorin.  Cane-sugar 
may  be  detected,  if  in  considerable  quantity,  by  the  taste. 
Cotton  devised  the  following  test:  10  c.c.  of  the  sample  are 
mixed  with  0.5  gram  of  powdered  ammonium  molybdate,  and 
10  c.c.  of  dilute  hydrochloric  acid  (i  to  10)  are  added.  In  a 
second  tube  10  c.c.  of  milk  of  known  purity  or  10  c.c.  of  a  6  per 
cent,  solution  of  milk-sugar  are  similarly  treated.  The  tubes 
are  then  placed  in  the  water-bath  and  the  temperature  gradually 
raised  to  about  80°.  If  sucrose  be  present,  the  milk  will  as- 
sume an  intense  blue  color,  while  genuine  milk  or  milk-sugar 
remains  unaltered  unless  the  temperature  be  raised  to  the  boil- 
ing-point.    According  to  Cotton,  the  reaction  is  well  marked 


MILK   AND   MILK   PRODUCTS 


217 


in  the  presence  of  as  little  as  i  gram  of  sucrose  to  a  liter  of  the 
milk,  and  6  grams  and  over  per  liter  are  usually  found  in  adul- 
terated samples.     (See  also  page  no.) 

The  quantitative  determination  is  made  by  the  methods 
described  in  connection  with  condensed  milk. 

General  Method  for  Colors  in  Milk. — Leach^^  has  devised  a 
general  method  for  detecting  colors  in  milk.  150  c.c.  of  the 
sample  are  coagulated  in  a  porcelain  basin,  with  the  addition 
of  acetic  acid  and  heating,  and  the  curd  separated  from  the 
whey.  The  curd  will  oft-en  collect  in  a  mass;  but  if  this  does 
not  occur,  it  must  be  freed  from  whey  by  straining  through 
muslin.  The  curd  is  macerated  for  several  hours  in  a  closed 
flask,  with  occasional  shaking,  with  ether  to  extract  fat.  An- 
natto  will  also  be  removed  by  it.  The  ether  and  curd  are 
separated  and  treated  as  follows : 


The  ether  is  evaporated,  the  residue 
mixed  with  a  httle  weak  solution 
of  sodium  hydroxid,  and  passed 
through  a  wet  fiher;  and  when  this 
^has  drained,  the  fat  is  washed  off 
and  the  paper  dried.  An  orange 
tint  shows  annatto,  which  may  be 
confirmed  by  a  drop  of  solution  of 
stannous  chlorid,  which  makes  a 
pink  spot. 


If  the  curd  be  colorless,  no  foreign 
coloring-matter  is  in  it;  if  orange 
or  brown,  it  should  be  shaken  with 
strong  hydrochloric  acid  in  a  test- 
tube. 


If  the  mass  turns 
blue  gradually, 
caramel  is  pro- 
bably present. 
The  whey 
should  be  ex- 
amined  for 
caramel  (see 
page  125). 


If  the  mass  turns 
pink  at  once,  an 
azo-color  is  indi- 
cated. 


Gelatin. — Stokes  detects  the  presence  of  gelatin  in  cream  or 
milk  as  follows:  10  c.c.  of  the  sample,  20  c.c.  of  cold  water, 
and  10  c.c.  of  acid  mercuric  nitrate  solution  (page  211)  are 
mixed,  shaken  vigorously,  allowed  to  stand  for  five  minutes,  and 
filtered.  If  much  gelatin  be  present,  it  will  be  impossible  to 
get  a  clear  filtrate.  A  portion  of  the  filtrate  is  mixed  with  an 
equal  bulk  of  saturated  aqueous  solution  of  picric  acid.  If  any 
gelatin  be  present,  a  yellow  precipitate  will  be  immediately 


2l8  FOOD   ANALYSIS 

produced.  Picric  acid  will  detect  the  presence  of  one  part  of 
gelatin  in  10,000  parts  of  water. 

Antiseptic  substances  are  largely  used,  especially  in  the 
warmer  season,  as  a  substitute  for  refrigeration.  Many  of 
these  are  sold  under  proprietary  names  which  give  no  indica- 
tion of  their  composition.  Preparations  of  boric  acid  and 
borax  were  at  one  time  the  most  frequent  in  use,  but  lately  for- 
malin, a  40  per  cent,  solution  of  formaldehyde  (methyl  alde- 
hyde), has  come  into  favor.  Sodium  benzoate  is  now  in  common 
use  as  a  preservative  of  cider,  fruit- jellies,  and  similar  articles, 
and  may,  therefore,  be  found  in  milk.  Salicylic  acid  is  not  so 
much  employed  as  in  former  years.  Sodium  carbonate  is  oc- 
casionally used  to  prevent  coagulation  due  to  slight  souring. 
A  mixture  of  boric  acid  and  borax  is  more  efficient  than  either 
alone.  The  quantity  generally  used  is  equivalent  to  about  0.5 
gram  of  boric  acid  per  liter.  Formaldehyde  is  the  most  effi- 
cient antiseptic.  In  the  proportion  of  0.125  g^'am  to  the  liter, 
it  will  keep  milk  sweet  for  a  week. 

Formaldehyde. — The  presence  of  this  body  may  sometimes 
be  detected  by  the  odor  developed  on  warming  the  milk. 
Hehner's  test  depends  upon  the  fact  that  when  milk  containing 
it  is  mixed  with  sulfuric  acid  containing  a  trace  of  ferric  salt  a 
blue  color  appears.  Richmond  &  Boseley  showed  that  the 
delicacy  of  the  test  is  much  increased  by  diluting  the  milk 
with  an  equal  bulk  of  water  and  adding  sulfuric  acid  of  90  to 
94  per  cent.,  so  that  it  forms  a  layer  underneath  the  milk. 
Under  these  conditions,  milk,  in  the  absence  of  formaldehyde, 
gives  a  slight  greenish  tinge  at  the  junction  of  the  two  liquids, 
while  a  violet  ring  is  formed  when  formaldehyde  is  present  even 
in  so  small  a  quantity  as  i  part  in  200,000  of  milk.  .  The  color 
is  permanent  for  two  or  three  days.  In  the  absence  of  formalde- 
hyde, a  brownish  color  is  developed  after  some  hours,  not  at 
the  junction  of  the  two  liquids,  but  lower  down  in  the  acid. 

The   phenylhydrazin   and   phloroglucol    tests   described   on 


MILK  AND  MILK  PRODUCTS  219 

page  83  are  applicable,  but  the  former  gives  a  grayish  green 
liquid  instead  of  the  blue  given  with  ordinary  formaldehyde 
solutions. 

Hydrochloric  acid  containing  a  small  amount  of  ferric  chlorid 
gives  a  characteristic  violet  with  quantities  of  formaldehyde 
not  over  one  part  per  1000.  The  test  is  applied  by  heating  i 
c.c.  of  the  sample  with  4  c.c.  of  strong  hydrochloric  acid.  If  a 
yellow  liquid  is  formed,  the  sample  should  be  diluted  two  or 
three  times  and  the  test  repeated.  Hydrochloric  acid  often 
contains  sufficient  ferric  chlorid  to  give  the  test.  The  addition 
of  0.25  gram  of  ferric  chlorid  to  1000  c.c.  of  pure  acid  will  be 
sufficient. 

Hehner  also  gives  the  following  test:  Some  of  the  milk  is 
distilled  and  to  the  distillate  one  drop  of  a  dilute  aqueous  so- 
lution of  phenol  is  added  and  the  mixture  poured  on  strong 
sulfuric  acid  contained  in  a  test-tube.  A  bright  crimson  zone 
appears  at  the  line  of  contact.  This  color  is  readily  seen  with 
I  part  of  formaldehyde  in  200,000  of  water.  If  there  is  more 
than  I  part  in  100,000,  there  is  seen  above  the  red  ring  a 
white,  milky  zone,  while  in  stronger  solutions  a  copious  white 
or  slightly  pink,  curdy  precipitate  is  obtained. 

The  reaction  succeeds  *  only  when  carried  out  as  described 
above;  the  phenol  must  first  be  mixed  with  the  solution  to  be 
tested,  and  the  mixture  poured  upon  the  sulfuric  acid.  Only 
a  trace  of  phenol  must  be  used,  and  if  it  be  first  dissolved  in 
the  acid  and  the  formaldehyde  solution  added,  no  color  is  ob- 
tained. The  precipitate  might  be  utilized  for  the  determina- 
tion of  the  strength  of  dilute  formalin  solutions. 

The  rate  at  which  formaldehyde  disappears  from  milk  has 
been  investigated  by  Hehner,  who  found  that  at  the  end  of  a 
week  none  could  be  detected  in  a  sample  to  which  had  been 
added  i  part  in  100,000;  after  two  weeks  none  could  be  de- 
tected in  a  sample  of  i  part  in  50,000;  after  three  weeks  only 
a  trace  could  be  detected  with  i  part  in  25,000. 


2  20  FOOD   ANALYSIS 

For  the  determination  of  the  formaldehyde,  the  sample  must 
be  distilled,  but  only  an  aliquot  portion  can  be  obtained.  B.  H. 
Smith  found  that  if  lOo  c.c.  of  milk  be  mixed  with  i  c.c.  of 
dilute  sulfuric  acid  (i  :  3),  one-third  of  the  formaldehyde  present 
will  pass  over  the  first  20  c.c.  of  distillate.  The  distillation  of 
milk  is  troublesome  owing  to  bumping  and  frothing.  Smith 
found  that  it  could  be  conducted  satisfactorily  in  a  500  c.c. 
Kjeldahl  flask  with   the  evaporating  burner  shown  on   page 

52. 

Sodium  Carbonate. — The  following  test  is  due  to  Schmidt. 

10  c.c.  of  the  milk  are  mixed  with  an  equal  volume  of  alcohol, 
and  a  few  drops  of  a  i  per  cent,  solution  of  rosolic  acid  added. 
Pure  milk  shows  merely  a  brownish-yellow  color,  but  in  the 
presence  of  sodium  carbonate  a  more  or  less  marked  rose-red 
appears.  The  delicacy  of  the  test  is  enhanced  by  making  a 
comparison  cylinder  with  the  same  amount  of  milk  known  to 
be  pure.  If  the  salt  is  present  in  considerable  amount,  it  may 
be  detected  by  the  increase  in  the  ash,  its  marked  alkaHnity  and 
effervescence  with  acid. 

Ahrastol. — i  c.c.  of  acid  mercuric  nitrate  solution  (page  211) 
is  added  to  20  c.c.  of  milk.  A  yellow  tint  indicates  abrastol. 
The  delicacy  of  the  test  may  be  increased  by  comparison  with 
an  untreated  portion  of  the  sample.  The  absence  of  other 
preservatives  should  be  assured.  The  extraction  method  given 
on  page  86  is  not  always  satisfactory  with  milk. 

Preservation  of  Milk-samples. — Formaldehyde  is  now  gen- 
erally used;  0.05  per  cent,  will  keep  milk  for  a  month  and 
larger  proportions  for  an  indefinite  period. 

Bevan  has,  however,  noted  the  fact  that  the  total  solids  of 
milk  containing  formaldehyde  are  always  higher,  and  that  the 
increase  is  much  greater  than  can  be  accounted  for,  even  as- 
suming that  all  the  formaldehyde  remains  in  the  residue. 

Detection  of  Boiled  Milk. — Dupouy  proposed  the  following 
method:    A  few  drops  of  a  solution  of  1-4  diamidobenzene  in 


MILK  AND  MILK  PRODUCTS  221 

water  are  added  to  5  c.c.  of  the  sample,  and  then  a  few  drops 
of  hydrogen  dioxid  solution.  Raw  milk  gives  a  blue  color; 
milk  that  has  been  heated  to  over  79°  gives  no  color.  The 
solution  of  diamidobenzene  must  be  freshly  prepared.  Rosier 
has  found  that  1-3-diamidobenzene  will  serve,  and  that  if  the 
blue  milk  be  shaken  with  amyl  alcohol,  the  blue  color  passes 
into  the  latter  and  is  more  stable.  These  tests  are  applicable 
for  distinguishing  between  pasteurized  and  sterilized  milks, 
as  the  reactivity  of  milk  is  lost  between  75°  and  80°. 

Faber  has  shown  that  raw  milk  may  be  distinguished  from 
boiled  milk  or  milk  that  has  been  heated  above  75°  by  the  fact 
that  such  treatment  coagulates  or  alters  the  albumin  so  that  if 
the  liquid  be  saturated  with  magnesium  sulfate,  the  albumin 
is  separated  along  with  the  albumin  casein. 

Richmond  &  Boseley  recommend  the  following  methods  to 
distinguish  new  milk  from  milk  which  has  been  steriHzed : 

(a)  100  c.c.  of  the  sample  are  allowed  to  stand  in  a  gradu- 
ated cylinder  for  six  hours  at  15.5°  and  the  percentage  of  cream 
noted.  If  less  than  2.5  per  cent,  of  cream  has  risen  for  each  i 
per  cent,  of  fat  in  the  milk,  the  milk  may  be  considered  suspi- 
cious; if  the  quantity  of  cream  falls  decidedly  below  2  per  cent, 
for  each  i  per  cent,  of  fat,  it  is  probable  that  sterilized  milk  is 
present. 

(b)  The  albumin  is  determined  by  means  of  magnesium 
sulfate.  If  less  than  0.35  per  cent,  is  found,  sterilized  milk 
may  be  considered  to  be  present. 

(c)  The  milk-sugar  is  determined  by  the  polarimeter,  and 
also  gravimetrically,  in  duplicate.  If  the  diflference  between 
the  two  estimations  be  more  than  0.2  per  cent.,  it  will  be  cor- 
roborative evidence  of  the  presence  of  sterilized  milk.  It  is 
doubtful  whether  a  proportion  of  sterilized  milk  much  below 
30  per  cent,  can  be  detected. 

The  following  figures,  by  Stewart,  show  the  percentage  of 
soluble  albumin  found  in  milk  raised  to  various  temperatures: 


222 


FOOD 

ANALYSIS 

Soluble  Albumin  in 

Soluble  Albumin  in 

Time  of 

Heating. 

F 

RESH  Milk. 

Heated  Milk. 

lo  minutes  at  60° 

0.423 

0.418 

30        " 

"  60° 

0-43S 

0.427 

10        " 

"  65° 

0-39S 

0.362 

30        " 

"  65° 

0-395 

o-SSS 

10        " 

"   70° 

0.422 

0.269 

30        " 

"   70° 

0.421 

0-253 

10        " 

"  75° 

0.380 

0.07 

30        " 

"  75° 

0.380 

0.05 

10       " 

"  80° 

0.37s 

none. 

30        " 

"  80° 

0-375 

none. 

CONDENSED  MILK 

The  form  of  condensed  milk  called  "evaporated  cream"  con- 
sists merely  of  whole  milk  concentrated  to  about  two-fifths 
of  its  bulk,  but  most  condensed  milks  contain  a  considerable 
amount  of  cane-sugar.  These  samples  represent,  usually, 
whole  milk  concentrated  to  about  one-third  or  two-sevenths 
of  its  original  volume.  A  small  amount  of  invert- sugar  may 
be  present.  Portions  of  the  lactose  may  crystallize  from  con- 
densed milk,  and  when  solutions  are  prepared  for  analysis, 
abnormal  polarimetric  reading  will  result  unless  the  liquid 
stands  for  some  hours  or  is  heated  for  a  short  time  to  100°.  The 
most  common  defect  in  condensed  milks  is  deficiency  in  fat, 
due  to  preparation  from  closely-skimmed  milks.  Preserva- 
tives (other  than  cane-sugar)  and  coloring-matters  are  rarely 
used,  nor  is  it  likely  that  foreign  fats  will  be  present. 

ANALYSES  OF  COMMERCIAL  CONDENSED  MILKS 


Total 

Solids. 

Fat. 

Proteids. 

Lactose. 

Sucrose. 

Ash. 

Analyst. 

36.7 

10.5 

9-7 

14.2 

none 

2.1 

Pearmain  and  Moor 

31.2 

9.6 

9.2 

10.9 

none 

1-5 

F.  J.  Aschman 

28.1 

8.8 

8.5 

9.8 

none 

1.8 

F.  J.  Aschman 

78.4 

9-3 

9.1 

134 

40.4 

2.0 

F.  J.  Aschman 

74.2 

9.0 

9-3 

10.2 

43-7 

1.9 

F.  J.  Aschman 

70.9 

1.4 

11.4 

14.6 

41.9 

1.6 

Pearmain  and  Moor 

The  sucrose  in  the  last  sample  was  determined  by  difiFerence. 


CONDENSED  MILK  223 

The  analysis  of  unsweetened  condensed  milks  is  conducted 
as  with  ordinary  milk,  the  sample  having  been  previously 
diluted  with  several  times  its  weight  of  water  heated  to  boil- 
ing, cooled,  and  made  up  to  a  definite  volume.  The  fat  may 
be  readily  estimated  by  the  L-B.  process. 

The  full  analysis  of  sweetened  condensed  milk  is  difficult, 
and  many  of  the  published  figures  are  erroneous.  The  cane- 
sugar  interferes  with  the  extraction  of  the  fat  by  solvents.  The 
same  difficulty  occurs  in  the  analysis  of  some  prepared  infant- 
foods,  such  as  mixtures  of  milk  with  malt  and  glucose. 

For  the  general  operations,  a  portion  of  the  well-mixed  con- 
tents of  a  freshly  opened  can  should  be  accurately  weighed, 
diluted  with  a  known  amount  of  water,  and  well  mixed,  from 
which  mass  the  portions  for  analysis  may  be  taken  and  the  re- 
sults calculated  to  the  original  sample.  50  grams  mixed  with 
150  c.c.  of  water  will  be  a  convenient  quantity.  For  the  polar- 
imetric  determination  of  lactose,  a  special  procedure  will  be 
necessary;  but  for  determination  of  solids,  ash,  total  proteids, 
and  total  reducing  sugars,  the  examination  may  be  made  as 
with  ordinary  milk  upon  this  diluted  sample. 

Fat. — The  Adams  method  is  not  satisfactory  under  ordinary 
conditions,  owing  to  the  sucrose.  Geisler  substituted  petro- 
leum spirit  or  a  mixture  of  this  with  anhydrous  ether,  extracting 
for  five  hours.  Bryant  has  obtained  better  results  with  carbon 
tetrachlorid,  which  is,  moreover,  safer. 

Some  analysts  have  advised  the  extraction  of  the  fat  from 
the  precipitate  obtained  with  copper  sulfate  (see  page  207). 
This  is  collected  on  fat-free  filter  paper  (hardened  paper  will 
answer),  washed  and  dried.  The  folded  filter  is  placed  on  a 
fat- free  thimble  and  extracted  with  carbon  tetrachlorid  for 
several  hours. 

The  Werner-Schmid  method  may  be  employed,  but  the  fat 
is  apt  to  be  contaminated  with  caramel.  It  should  be  dissolved 
in  anhydrous  ether,  by  which  the  caramel  will  be  left  adher- 


224  FOOD   ANALYSIS 

ing  to  the  glass;  and  after  washing  this  with  a  httle  more  ether, 
it  should  be  dried  and  weighed  and  the  fat  determined  by  dif- 
ference. 

The  estimation  of  fat  by  centrifugal  method  is  seriously 
impeded  by  the  carbonization  of  the  sucrose,  and  various 
methods  have  been  proposed  for  overcoming  this  difhculty. 
Leach  devised  the  following  method,  which  he  finds  to  be  more 
trustworthy  than  ordinary  extractions  with  solvents.  I^each 
applied  the  process  to  a  centrifugal  method  not  identical  with 
the  one  described  on  page  203,  but  this  is  not  important: 

25  c.c.  of  diluted  material  are  measured  into  the  test-bottle, 
water  added  sufficient  to  fill  it  to  the  beginning  of  the  stem, 
and  then  4  c.c.  of  the  copper  sulfate  solution  used  for  sugar 
determination,  the  mixture  allowed  to  stand  for  a  few  minutes, 
then  shaken  well,  and  the  precipitate  settled  by  whirling  the 
bottle  in  the  machine.  The  supernatant  liquid  is  drawn  off. 
The  precipitate  is  washed  twice  with  water  by  the  same  method, 
settling  the  precipitate  in  each  case  by  the  use  of  the  centrifuge, 
taking  care  that  the  mass  is  well  stirred  with  the  water  before 
each  whirling.  After  the  second  washing,  about  15  c.c.  of 
water  are  put  in,  the  precipitate  stirred  up,  the  amyl  alcohol 
mixture  added,  then  the  sulfuric  acid,  as  directed  on  page  203, 
the  mixture  whirled,  and  the  fat  measured.  The  percentage 
of  fat  will  be  that  based  on  the  25  c.c.  used,  and  the  amount  in 
the  original  sample  may  be  calculated  from  the  dilution. 

Cochran's  method. — This  is  based  on  the  solution  of  the  curd 
by  the  DeLaval  method  and  solution  of  the  fat  in  ether.  It  may 
be  appHed  by  means  of  the  L-B.  bottles  and  centrifuge,  or  with 
a  special  flask  (which  does  not  require  a  centrifuge)  devised  by 
Cochran.  If  L-B.  bottles  are  used,  the  reading  must  be  multi- 
plied by  3,  since  only  5  c.c.  of  the  sample  are  taken.  The  pro- 
cess is  especially  adapted  to  sweetened  condensed  milk  and 
cereal  foods  containing  fat.  The  fat  of  normal  cereals  can  be 
accurately  determined  by  it.     The  curd  is  dissolved  by  a  mixture 


CONDENSED   MILK  225 

of  equal  parts  sulfuric  acid  and  80  per  cent,  acetic  acid.  This 
mixture  may  be  made  beforehand  or  the  acids  may  be  added 
in  succession  to  the  material  in  the  bottle  or  flask.  With  the 
flask,  all  materials  must  be  added  through  the  side-tube. 

Ordinary  milk  is  taken  undiluted,  but  condensed  milk  is 
diluted.  Sweetened  condensed  milk  is  diluted  with  3  times  its 
weight  of  water;  unsweetened  condensed  with  an  equal  weight 
of  water. 

5  c.c.  of  the  prepared  sample  are  introduced  into  the  flask 
by  means  of  the  side-tube,  5  c.c.  of  the  acid  mixture  added  slowly 
with  shaking,  taking  care  that  the  liquid  does  not  get  into  the 
graduated  tube.  If  the  liquid  becomes  dark  brown  and  free 
from  lumps  of  undissolved  curd,  the  flask  is  allowed  to  cool  and 
4  c.c.  of  ether  added  (common  ether  will  answer).  If  the  mix- 
ture produced  by  the  acid  is  lumpy,  the  flask  is  set  in  tepid 
water,  heated  gradually  (not  above  80°)  and  shaken  gently  until 
all  flocculent  matter  is  dissolved.  Care  must  be  taken  not  to 
continue  this  heating  until  masses  of  caramel  are  formed,  as 
this  will  prevent  correct  results  being  obtained. 

When  the  flocculent  matter  has  disappeared  (the  liquid  will 
in  any  case  show  some  turbidity  from  the  emulsion  of  fat),  the 
flask  is  cooled  and  ether  added  as  noted  above.  The  flask  is 
well  shaken  to  cause  the  ether  to  take  up  all  the  fat,  taking  care 
not  to  bring  the  liquid  up  into  the  graduated  tube.  When  the 
fat  is  dissolved,  the  flask  is  placed  in  water  at  about  40°,  kept 
still  and  the  temperature  raised  slowly  until  all  ether  is  vaporized, 
then  rapidly  until  the  boiling-point  is  reached,  and  this  con- 
tinued until  the  solution  ceases  to  bubble,  and  the  fat  forms  a 
clear  layer  on  the  surface  of  the  dark  but  clear  acid  solution. 
The  flask  should  not  be  skaken  while  evaporating  the  ether. 
Water  heated  to  nearly  boiling  is  now  run  cautiously  into  the 
side-tube  until  the  flask  is  three-quarters  full.  If  any  fat  is  in 
the  side-tube,  it  may  be  removed  by  blowing  gently  into  it. 
If  the  liquid  is  producing  but  few  bubbles,  more  hot  water  should 


226  FOOD   ANALYSIS 

be  run  in  until  all  the  fat  is  within  the  limits  of  the  graduation. 
If  the  bubbling  is  still  violent  when  the  tube  is  only  three-quarters 
full,  the  lower  half  of  the  flask  should  be  cooled  by  immersion 
in  cold  water,  when  the  bubbling  will  nearly  cease,  and  the  fat 
may  then  be  raised  into  the  neck  by  adding  more  hot  water. 
The  flask  may  stand  for  a  minute,  if  necessary  to  allow  the  fat 
column  to  unite,  but  it  should  be  measured  as  soon"  as  possible. 
The  graduation  is  percentage  of  fat  by  weight,  based  on  5  c.c. 
of  milk  (say  5.16  grams).  If  the  sample  has  been  diluted,  the 
reading  must  be  increased  by  the  factor  of  dilution. 

The  process  is  easy  of  accurate  operation  and  is  especially 
adapted  to  materials  that  do  not  yield  fat  to  common  extraction 
methods.  The  special  point  is  to  avoid  prolonged  or  excessive 
heating  with  the  acid  liquid,  as  this  will  produce  lumps  of  partly 
carlx)nized  matter.  If  these  form,  the  operation  must  be  dis- 
continued and  the  flask  cleaned  promptly.  This  lumpy  ma- 
terial should  be  distinguished  from  a  brown  flocculent  matter 
which  rests  between  the  acid  and  ether  layer  at  the  early  part 
of  the  operation,  but  which  disappears  later. 

For  the  examination  of  malted  cereals,  1.72  grams  are  taken 
and  introduced  by  the  side-tube,  taking  care  that  no  more  ma- 
terial adheres  than  can  be  washed  into  the  flask  by  not  more 
than  5  c.c.  of  water.  The  mass  is  mixed  thoroughly  by  shaking, 
3  c.c.  of  the  acid  mixture  are  introduced  and  the  process  is 
carried  out  as  described,  taking  especial  care  not  to  overheat. 
The  volume  of  fat  multiplied  by  3  gives  percentage. 

Most  malted  cereals  are  easily  treated  by  the  method,  but 
some  contain  insoluble  cellular  matter.  With  care,  this  will 
not  interfere.  Sometimes  previous  treatment  with  diluted  sul- 
furic acid  will  render  the  material  more  tractable. 

The  flasks  should  be  cleaned  promptly.  The  chromic-sul- 
furic  mixture  (see  page  51)  is  the  best. 

Sugars. — If  regard  is  to  be  given  to  the  presence  of  invert- 


CONDENSED  MILK  227 

sugar,  a  special  method  must  be  followed.  The  processes 
first  given  consider  lactose  and  sucrose  only. 

Lactose. — The  heating  employed  in  the  manufacture  of  con- 
densed milk  may  reduce  the  rotatory  power  of  the  sugar  suf- 
ficiently to  cause  error  in  the  polarimetric  method.  The  reducing 
power  with  alkaline  copper  solutions  is  not  seriously  affected. 

Sucrose. — This  determination  may  be  made  by  difference; 
that  is,  subtracting  the  sum  of  the  other  ingredients  from  the 
total  solids.  This  will  serve  for  ordinary  inspection  purposes, 
since  the  amount  present  is  almost  always  large,  generally 
more  than  the  total  of  milk-solids,  and  an  error  even  of  several 
per  cent,  does  not  affect  the  judgment  as  to  the  wholesomeness 
of  the  sample.  Exact  work  requires,  however,  that  the  cane- 
sugar  be  determined  directly,  and  several  processes  have  been 
devised  for  the  purpose.  Sucrose  exerts  but  little  action  on 
Fehling's  solution,  but  invert-sugar  acts  powerfully,  and  some 
processes  depend  on  determining  the  reducing  power  before 
and  after  inversion.  Since  the  polarimetric  reading  is  also 
markedly  changed  by  the  inversion,  the  difference  in  polariza- 
tion may  be  employed.  Processes  of  fermentation  may  be  so 
conducted  as  to  remove  the  sucrose  (also  any  form  of  glucose) 
while  the  lactose  is  unafifected.  This  method  is  chiefly  valuable 
for  recognizing  invert-sugar  or  either  of  its  constituents. 

When  inversion  methods  are  used,  they  must  be  such  as  to 
secure  prompt  inversion  of  the  sucrose  without  affecting  the 
lactose.  Experiment  shows  that  citric  acid  and  invertase  are 
the  most  suitable  agents.  Stokes  &  Bodmer  have  worked  out 
the  citric  acid  method  substantially  as  follows: 

25  c.c.  of  the  diluted  sample  are  coagulated  by  addition  of  i 
per  cent,  of  citric  acid,  without  heating,  and  made  up  to  200  c.c. 
plus  the  volume  of  the  precipitated  fat  and  proteids  (see  p.  212). 
The  liquid  portion,  which  now  measures  200  c.c,  is  passed 
through  a  dry  filter.  The  reducing  power  with  alkaline  copper 
solutions  is  determined  at  once  upon  50  c.c.  of  this  filtrate.    To 


2  28  FOOD   ANALYSIS 

another  50  c.c,  i  per  cent  of  citric  acid  is  added,  the  solution 
boiled  at  least  30  minutes/^  and  the  reducing  power  also  deter- 
mined. The  increase  over  that  of  the  first  solution  is  due  to  the 
invert-sugar  formed  by  the  action  of  the  citric  acid  on  the 
sucrose.  It  is  necessary  to  bear  in  mind  that  the  reducing 
equivalents  of  lactose  and  invert-sugar  are  not  the  same. 
Volumetric  method  may  be  employed. 

The  following  method  is  based  on  the  difference  in  polari- 
metric  reading  before  and  after  action  of  invertase.  75  c.c.  of  the 
diluted  milk  are  placed  in  a  100  c.c.  flask,  diluted  to  about  80  c.c, 
heated  to  boiling,  to  correct  birotation,  cooled,  and  10  c.c.  of  acid 
mercuric  nitrate  solution  added.  The  mixture  is  made  up  to 
100  c.c,  well  shaken,  filtered  through  a  dry  filter,  and  the  polari- 
metric  reading  taken  at  once.  It  will  be  the  sum  of  the  effect 
of  the  two  sugars.  The  volume  of  the  sugar-containing  liquid 
is  calculated  by  allowing  for  the  precipitated  proteids  and  fat, 
as  described  on  page  212. 

50  c.c  of  the  filtrate  are  placed  in  a  flask  marked  at  55  c.c, 
a  piece  of  litmus  paper  dropped  in,  and  the  excess  of  nitric 
acid  cautiously  neutralized  by  sodium  hydroxid  solution.  The 
liquid  is  then  faintly  acidified  by  a  single  drop  of  acetic  acid 
(it  must  not  be  alkaline) ,  a  few  drops  of  an  alcoholic  solution  of 
thymol  are  added,  and  then  2  c.c.  of  a  solution  of  invertase, 
prepared  by  grinding  half  a  cake  of  ordinary  compressed  yeast 
with  10  c.c  of  water  and  filtering.  The  flask  is  corked  and 
allowed  to  remain  at  a  temperature  of  35°  to  40°  for  24  hours. 
The  cane-sugar  will  be  inverted,  while  the  milk-sugar  will  be 
unaffected.  The  flask  is  filled  to  the  mark  (55  c.c)  with  washed 
aluminum  hydroxid  and  water,  mixed,  filtered,  and  the  polari- 
metric  reading  taken.  The  amount  of  cane-sugar  can  be  de- 
termined from  the  difference  in  the  two  readings  by  the  formula 
on  page  120. 

A  powerful  solution  of  invertase  may  be  prepared  by  the 
method  recommended  by  O'Sullivan  and  Tompson.     Brewer's 


CONDENSED   MILK  229 

yeast  is  allowed  to  stand  at  a  temperature  of  15°  for  a  month. 
The  liquid  is  filtered  and  sufficient  alcohol  added  to  give 
about  12  per  cent,  of  absolute  alcohol.  After  a  few  days  the 
liquid  is  filtered  and  is  ready  for  use.  The  alcohol  acts  as  a 
preservative. 

Bigelow  and  McElroy  propose  the  following  routine  method 
for  the  determination  of  the  sugars,  including  invert-sugars,  in 
condensed  milk.     The  solutions  used  are: 

Acid  Mercuric  lodid. — Mercuric  chlorid,  1.35  grams;  potas- 
sium iodid,  3.32  grams;  glacial  acetic  acid,  2.c.c.;  water,  64  c.c. 

Alumina-cream. — See  page  118. 

The  entire  contents  of  the  can  are  transferred  to  a  porcelain 
dish  and  thoroughly  mixed.  A  number  of  portions  of  about  25 
grams  are  weighed  carefully  in  100  c.c.  flasks.  Water  is  added 
to  two  of  the  portions,  and  the  solutions  boiled.  The  flasks  are 
then  cooled,  clarified  by  means  of  a  small  amount  of  the  acid 
mercuric  iodid  and  alumina-cream,  made  up  to  mark,  filtered, 
and  the  polarimetric  reading  noted.  Other  portions  of  the  milk 
are  heated  in  the  water-bath  to  55°;  one-half  of  a  cake  of  com- 
pressed yeast  is  added  to  each  flask  and  the  temperature  main- 
tained at  55°  for  five  hours.  Acid  mercuric  iodid  and  alumina- 
cream  are  then  added,  the  solution  cooled  to  room  temperature, 
made  up  to  mark,  mixed,  filtered,  and  polarized.  The  amount 
of  cane-sugar  is  determined  by  formula  on  page  1 20.  Correction 
for  the  volume  of  precipitated  solids  may  be  made  by  the  double- 
dilution  method  (p.  21).  The  total  reducing  sugar  is  estimated 
in  one  of  the  portions  by  one  of  the  reducing  methods,  and  if 
the  sum  of  it  and  the  amount  of  cane-sugar  obtained  by  in- 
version is  equal  to  that  obtained  by  the  direct  reading  of  both 
sugars  before  inversion,  no  invert-sugar  is  present.  If  the 
amount  of  reducing  sugar  seems  to  be  too  great,  the  milk-sugar 
must  be  re-determined  as  follows:  250  grams  of  the  condensed 
milk  are  dissolved  in  water,  the  solution  boiled,  cooled  to  80°, 
a  solution  of  about  4  grams  of  glacial  phosphoric  acid  added, 


230  FOOD  ANALYSIS 

the  mixture  kept  at  80°  for  a  few  minutes,  then  cooled  to  room 
temperature,  made  up  to  mark,  shaken,  and  filtered.  It  may 
be  assumed  that  the  volume  of  the  precipitate  is  equal  to  that 
obtained  by  mercuric  iodid  solution.  Enough  sodium  hydroxid 
is  then  added  to  not  quite  neutralize  the  free  acid,  and  sufficient 
water  to  make  up  for  the  volume  of  the  solids  precipitated  by 
the  phosphoric  acid.  The  mixture  is  then  filtered  and  the  fil- 
trate is  measured  in  portions  of  100  c.c.  into  200  c.c.  flasks.  A 
solution  containing  20  milligrams  of  potassium  fluorid  and  half 
a  cake  of  compressed  yeast  is  added  to  each  flask,  and  the  mix- 
ture allowed  to  stand  for  10  days  at  a  temperature  between  25° 
and  30°.  The  invert- sugar  and  cane-sugar  are  fermented  and  re- 
moved by  the  yeast  in  the  presence  of  a  fluorid,  while  milk-sugar 
is  unaffected.  The  flasks  are  filled  to  the  mark  and  the  milk- 
sugar  determined  either  by  reducing  or  by  the  polariscope. 
The  amount  of  copper  solution  reduced  by  the  lactose  and  invert- 
sugar,  less  the  equivalent  of  lactose  remaining  after  fermenta- 
tion, is  due  to  invert-sugar. 

BUTTER 

Butter  is  a  mixture  of  fat,  water,  and  curd.  The  water  con- 
tains milk-sugar  and  the  salts  of  the  milk.  Common  salt  is 
usually  present,  being  added  after  the  churning.  Artificial 
coloring  is  frequently  used. 

Butter-fat  is  distinguished  from  other  animal  fats  in  that  it 
contains  a  notable  proportion  of  acid  radicles  with  a  small 
number  of  carbon  atoms.  Thus,  about  91  per  cent,  consists 
of  palmitin  and  olein  and  the  remainder  of  butyrin  and  ca- 
proin,  along  with  small  amounts  of  caprylin,  caprin,  myristin, 
and  some  others.  According  to  the  experiments  of  Hehner 
&  Mitchell,  stearin  is  present  only  in  very  small  quantity. 
The  exact  arrangement  of  the  constituents  is  unknown. 

The  composition  of  commercial  butter  usually  varies  within 
the  following  limits: 


BUTTER  231 

Fat, 78  per  cent,  to  94  per  cent. 

Curd, I         "         "3 

Water, 5         "        "  i4 

Salt, o        "        "7 

Butter  containing  over  40  per  cent,  of  water  is  sometimes 
sold.  Such  samples  are  pale  and  spongy,  lose  weight,  and 
become  rancid  rapidly. 

The  official  methods  of  the  A.  O.  A.  C.  for  the  analysis  of 
butter  are  as  follows: 

Preparation  of  the  Sample. — If  large  quantities  of  butter 
are  to  be  sampled,  a  butter  trier  or  sampler  may  be  used. 
The  portions  thus  drawn,  about  500  grams,  are  to  be  per- 
fectly melted  in  a  closed  vessel  at  as  low  a  temperature  as 
possible,  and  when  melted  the  whole  is  to  be  shaken  violently 
for  some  minutes  until  the  mass  is  homogeneous  and  suffi- 
ciently solidified  to  prevent  the  separation  of  the  water  and  fat. 
A  portion  is  then  poured  into  the  vessel  from  which  it  is  to  be 
weighed  for  analysis,  and  should  nearly  or  quite  fill  it.  This 
sample  should  be  kept  in  a  cold  place  until  analyzed. 

Water. — From  1.5  to  2.5  grams  are  dried  to  constant  weight 
at  the  temperature  of  boiHng  water,  in  a  dish  with  flat  bottom, 
having  a  surface  of  at  least  20  sq.  cm.  The  use  of  clean  dry 
sand  or  asbestos  with  the  butter  is  admissible,  and  is  necessary 
if  a  dish  with  round  bottom  be  employed. 

Fat. — The  dry  butter  from  the  water  determination  is  dis- 
solved in  the  dish  with  absolute  ether  or  with  petroleum  spirit 
(sp.  gr.  0.680).  The  contents  of  the  dish  are  then  transferred 
to  a  weighed  Gooch  crucible  with  the  aid  of  a  wash-bottle  filled 
with  the  solvent,  and  are  washed  until  free  from  fat.  The  cruci- 
ble and  contents  are  heated  at  the  temperature  of  boiling  water 
till  the  weight  is  constant. 

The  fat  may  also  be  determined  by  drying  the  butter  on 
asbestos  or  sand,  and  extracting  by  anhydrous  alcohol- free 
ether.    After  evaporation  of  the  ether  the  extract  is  heated 


232  FOOD   ANALYSIS 

to  constant  weight  at  the  temperature  of  boiling  water  and 
weighed. 

Casein,  Ash,  and  Chlorin. — The  crucible  containing  the 
residue  from  the  fat  determination  is  covered  and  heated, 
gently  at  first,  gradually  raising  the  temperature  to  just  below 
redness.  The  cover  is  removed  and  the  heat  continued  until 
the  material  is  white.  The  loss  in  weight  represents  casein, 
and  the  residue  mineral  matter.  In  this  mineral  matter  dis- 
solved in  water  slightly  acidulated  with  nitric  acid,  chlorin 
may  be  determined  gravimetrically  with  silver  nitrate,  or,  after 
neutralization  with  calcium  carbonate,  volumetrically,  using 
potassium  chromate  as  indicator. 

Salt. — About  10  grams  are  weighed  in  a  beaker  in  por- 
tions of  about  I  gram  at  a  time  taken  from  different  parts  of 
the  sample.  Hot  water  (about  20  c.c.)  is  now  added  to  the 
beaker,  and  after  the  butter  has  melted,  the  mass  is  poured 
into  the  bulb  of  a  separating  funnel,  which  is  then  closed  and 
shaken  for  a  few  moments.  After  standing  until  the  fat  has 
all  collected,  the  water  is  allowed  to  run  into  an  Erlenmeyer 
flask,  with  care  not  to  let  fat  globules  pass.  Hot  water  is  again 
added  to  the  beaker,  and  the  extraction  is  repeated  from  ten 
to  fifteen  times,  using  each  time  from  10  to  20  c.c.  of  water. 
The  resulting  washings  contain  all  but  a  mere  trace  of  the  salt 
originally  present  in  the  butter.  The  chlorin  is  determined 
volumetrically  in  the  filtrate  by  means  of  standard  silver  nitrate 
and  potassium  chromate  indicator  and  calculated  to  sodium 
chlorid. 

Adulteration  with  Foreign  Fats. — The  chief  adulteration  of 
butter  consists  in  the  substitution  of  foreign  fats,  especially  the 
product  known  as  oleomargarin. 

When  fats  are  saponified  and  the  soap  treated  with  acid,  the 
individual  fatty  acids  are  obtained.  It  is  upon  the  recognition 
of  the  peculiar  acid  radicles  existing  in  butter  that  the  most 
satisfactory  method  of  distinguishing  it  from  other  fats  is  based. 


BUTTER  233 

Since  the  relative  proportion  of  these  radicles  differs  in  dif- 
ferent samples,  the  quantitative  estimation  cannot  be  made 
with  accuracy;  but  when  the  foreign  fats  are  substituted  to 
the  extent  of  20  per  cent,  or  more,  the  adulteration  can  be 
detected  with  certainty  and  an  approximate  quantitative  deter- 
mination made. 

The  detection  of  adulteration  of  butter-fat  by  other  fats  is 
generally  carried  out  by  the  determination  of  the  volatile  acid, 
but  some  other  confirmatory  processes  are  occasionally  em- 
ployed. The  data  for  interpreting  results  will  be  found  in  the 
table  on  page  165. 

Volatile  Acids. — The  glycerol-soda  method  (page  143)  is 
sufficient  for  the  purpose.  No  advantage  will  result  from 
using  the  tedious  method  with  alcoholic  solution;  indeed, 
under  ordinary  circumstances  the  latter  is  probably  less  accu- 
rate. 

Butter  (5  grams)  yields  a  distillate  requiring  from  24  to  34 
c.c.  of  decinormal  alkali.  Several  instances  have  been  pub- 
lished in  which  genuine  butter  has  given  a  figure  as  low  as 
22.5  c.c,  but  such  results  are  uncommon.  The  materials 
employed  in  the  preparation  of  oleomargarin  yield  a  distillate 
requiring  less  than  i  c.c.  of  alkali.  Commercial  oleomargarin 
is  usually  churned  with  milk  in  order  to  secure  a  butter  flavor, 
and,  thus  acquiring  a  small  amount  of  butter-fat,  yields  dis- 
tillates capable  of  neutralizing  from  i  to  2  c.c.  of  alkali. 

If  coconut  oil  (see  page  165)  has  been  used  in  the  prepara- 
tion of  the  oleomargarin,  the  figure  will  be  higher,  but  there 
will  still  be  no  difficulty  in  distinguishing  pure  butter. 

Saponification  Value. — In  the  absence  of  coconut  oil,  the 
saponification  value  will  give  valuable  indications  as  to  the 
purity  of  a  butter  sample.  It  is  possible  to  make  oleomar- 
garin, by  the  addition  of  coconut  oil,  which  would  have  the 
same  saponification  value  as  pure  butter. 

Specific  Gravity. — According  to  Skalweit,  the  greatest  dif- 


234  FOOD   ANALYSIS 

erences  between  the  specific  gravity  of  butter  and  its  adulter- 
ants are  found  at  a  temperature  of  35°,  but  the  determina- 
tion is  more  conveniently  made  at  the  temperature  of  boiling 
v^ater.  The  Sprengel  tube  or  Westphal  balance  may  be  em- 
ployed for  the  purpose. 

The  determination  of  the  Reichert  number  will  usually  give 
sufficient  information  as  to  the  nature  of  a  butter  sample.  In 
doubtful  cases  it  may  be  of  advantage  to  apply  other  tests  as 
corroborative  evidence.  The  determination  of  soluble  and 
insoluble  acids  may  be  employed,  but  Valenta's  test  and  the 
refractometric  examination  are  especially  mentioned  as  fur- 
nishing results  with  little  trouble  in  a  short  time. 

Soluble  and  Insoluble  Acids. — The  proportion  of  insoluble 
acids  in  butter  is  usually  about  87.5  per  cent,  and  of  soluble 
acids,  calculated  as  butyric,  about  5  per  cent.  The  insoluble 
acids  may  be  present  to  the  extent  of  88.5  per  cent.,  but,  ac- 
cording to  most  authorities,  they  will  only  reach  90  per  cent, 
in  the  presence  of  adulterants.  These  figures  apply  to  fresh 
samples.  After  keeping  until  rancidity  has  developed  the 
proportion  of  insoluble  acids  may  be  increased  i  per  cent,  or 
more. 

Mixtures  of  butter,  oleomargarin,  and  coconut  oil  may  have 
the  same  proportion  of  insoluble  acids  as  butter- fat. 

Valenta^s  Test. — Jones  recommends  the  employment  of  a 
standard  butter-fat  with  which  to  standardize  each  fresh 
batch  of  acid,  and  dilution  of  the  acid  to  such  a  point  that  the 
turbidity  temperature  with  this  fat  is  60°.  In  this  way  the 
results  are  comparable  with  those  of  previous  tests. 

With  such  acid,  oleomargarin  gave  temperatures  from  95° 
to  106°,  and  generally  from  100°  to' 102°. 

Milk  test. — The  following  test  was  proposed  by  Waferhouse  ** : 
50  c.c.  of  fresh  whole  milk  are  placed  in  a  100  c.c.  beaker,  heated 
nearly  to  boiling  and  a  lump  of  the  sample  (5  to  10  grams) 
stirred  in,  preferably  with  a  wooden  rod,  until  the  fat  is  melted. 


BUTTER  235 

The  beaker  is  placed  in  cold  water  and  the  stirring  continued 
until  the  temperature  falls  to  the  solidifying  point  of  the  fat. 
Butter  fat  will  be  granular  and  not  easily  collected  into  a  lump, 
but  oleomargarin  will  collect  readily. 

Rejractometric  Examination. — This  is  most  satisfactorily 
made  by  the  oleorefractometer  or  the  butyrorefractometer. 
Jean  prepares  the  sample  for  examination  in  the  former  as 
follows:  30  grams  of  butter  are  melted  in  a  porcelain  dish  at 
a  temperature  not  exceeding  50°,  stirred  well  with  a  pinch  or 
two  of  gypsum,  and  allowed  to  settle  out  at  the  same  temper- 
ature. The  supernatant  fat  is  decanted  through  a  hot-water 
funnel  plugged  with  cotton  and  poured  while  warm  into  the 
prism  of  the  apparatus,  stirred  with  the  thermometer  until  the 
fat  has  cooled  to  45°,  and  the  deviation  observed.  Ether  must 
not  be  used  for  the  solvent,  as  minute  traces  of  it  seriously 
influence  the  result. 

The  following  table  is  a  summary  of  the  results  obtained  by 
several  observers,  including  Jean  and  Pearmain.  The  oleo- 
refractomer  was  different  from  those  shown  on  page  154,  but 
the  figures  have  a  relative  value: 

Degrees  in 
Oleorefractometer  . 

Butter, — 25  to  — 34,  usually  — 30 

Oleomargarin, — 13  to  — 18 

Butter  with  10  p.  c.  oleomargarin  ( — 17),     — 28 

Butter  with  50  p.  c.  oleomargarin, — 23 

Lard, — 8  to  — 14 

Coconut  oil, — 59 

Arachis  oil, 3-5  to  7 

Cottonseed  oil, 12  to  23 

Cottonseed  "stearin," 25 

De  Bruyn  found  as  low  as  — 21  in  butter  from  animals  fed 
on  linseed  cakes.  A  mixture  of  coconut  oil  and  oleomargarin 
may  be  made  having  the  same  refractive  power  as  pure  butter. 
Evidently,  therefore,  it  is  not  possible  from  this  datum  alone 
to  state  that  a  given  sample  is  pure  butter,  but  a  sample  ex- 


236  FOOD   ANALYSIS 

hibiting  a  refraction  of  — 20°  or  under  may  be  pronounced 
adulterated. 

Zeiss'  butyrorefractometer  is  now  much  used,  the  resuhs 
being  of  service  in  sorting  samples  and  as  confirmation. 

Commercial  forms  of  oleomargarin  and  butter  exhibit  char- 
acteristic differences  on  heating,  which  may  be  utilized  for 
rapidly  sorting  a  collection  of  samples.  When  butter  is  heated 
in  a  small  tin  dish  directly  over  a  gas  flame,  it  melts  quietly, 
foams,  and  may  run  over  the  dish.  Oleomargarin,  under 
the  same  conditions,  sputters  noisily  as  soon  as  heated  and 
foams  but  little.  Even  mixtures  of  butter  and  other  fats  show 
this  sputtering  action  to  a  considerable  extent.  The  effect- 
depends  upon  the  condition  in  which  the  admixed  water  exists, 
and  the  test  is  not  applicable  to  butter  which  has  been  melted 
and  reworked  (renovated  or  process  butter). 

An  alcoholic  solution  of  sodium  hydroxid,  heated  for  a 
moment  with  butter,  and  then  emptied  into  cold  water,  gives 
a  distinct  odor  of  pineapples,  while  oleomargarin  gives  only 
the  alcoholic  odor. 

Renovated  Butter. — So-called  "process"  or  "renovated" 
butter,  made  by  rendering  old  or  inferior  samples,  purifying 
the  fat,  coloring,  salting,  and  molding  it,  is  now  a  familiar  com- 
mercial article.  Process  butter  when  heated  in  a  dish  sputters 
with  but  little  foaming,  as  does  oleomargarin;  but  yields  with 
alcoholic  soda  the  pineapple  odor,  as  does  butter.  The  fat  of 
process  butter  gives  refractometric  data  and  Reichert-Meissl 
number  similar  to  those  of  ordinary  dairy  butter,  but  is  said 
to  give  a  different  figure  with  Valenta's  test.  If,  therefore, 
a  sample  sputters  in  the  pan,  but  gives  the  other  reactions  for 
butter,  as  just  noted,  it  may  be  assumed  to  be  process  butter. 
Hess  &  Doolittle  state  that  the  curd  of  process  butter  has 
characteristic  qualities,  and  propose  the  following  method  fcr 
detecting  it: 

50  grams  of  the  sample  are  melted  in  a  beaker  at  about 


BUTTER  237 

50°.  Ordinary  butter  yields  a  clear  fat  almost  as  soon  as 
melted,  while  with  process  butter  the  fat  may  remain  turbid 
for  a  long  while.  When  the  curd  has  largely  settled,  as  much 
of  the  fat  is  poured  off  as  possible,  and  the  remaining  mix- 
ture is  thrown  on  a  wet  filter,  by  which  the  water  will  drain 
away,  carrying  the  soluble  proteids  and  salt.  A  few  drops  of 
acetic  acid  are  added  to  the  filtrate  and  the  mixture  is  boiled. 
The  filtrate  from  ordinary  butter  gives  a  slight  milkiness,  but 
that  from  process  butter  gives  a  flocculent  precipitate. '  Quan- 
titative examination  is  made  by  dissolving  50  grams  of  the 
sample  in  ether;  if  it  is  ordinary  butter,  the  curd  is  so  finely 
divided  that  it  remains  suspended  for  some  time.  As  much 
as  possible  of  the  solution  is  decanted  and  the  mass  transferred 
to  a  separator,  the  casein,  water,  and  salt  removed,  and  the  re- 
mainder washed  three  times,  at  least,  with  ether  to  remove  the 
fat.  The  curd  is  collected  on  a  filter,  washed  with  water,  and 
the  nitrogen  determined  by  treating  the  precipitate  with  the 
filter  by  the  Kjeldahl- Gunning  method.  The  filtrate  from  the 
curd  is  made  sHghtly  acid  with  acetic  acid,  boiled,  the  pre- 
cipitated proteids  collected  on  a  filter,  and  the  total  nitrogen 
determined.  The  factor  6.38  may  be  used  in  each  case  for 
converting  the  nitrogen  into  proteids. 

A  distinction  between  ordinary  and  process  butter  may 
often  be  made  by  microscopic  examination  under  polarized 
light  with  crossed  nicols  (i.  e.,  dark  field),  when  the  process 
butter  appears  mottled,  owing  to  the  presence  of  crystals. 

Butter  Colors. — Butter  and  butter  substitutes  are  usually 
artificially  colored.  Preparations  of  turmeric  and  annatto  or 
azo-colors  allied  to  methyl-orange  are  used.  The  latter  forms 
may  be  detected  by  the  test  devised  by  Geisler.  A  small  amount 
of  the  sample,  or,  better,  the  fat  filtered  from  it,  is  mixed 
on  a  porcelain  plate  with  a  little  fuller's  earth.  Azo-colors 
give  promptly  a  red  mass,  while  if  they  are  not  present,  the  mix- 
ture becomes  only  yellow  or  light  brown.     All  samples  of 


238  FOOD  ANALYSIS 

fuller's  earth  are  not  equally  active,  and  tests  should  be  made 
with  different  samples  by  using  fat  known  to  contain  the  azo- 
compound  until  a  good  specimen  of  the  earth  is  secured. 

For  the  detection  of  very  minute  quantities  of  the  color,  the 
sample  may  be  dissolved  in  light  petroleum,  and  the  fuller's 
earth  added  to  the  solution,  when  the  pink  color  will  appear 
as  a  distinct  ring  or  zone  at  the  edge  of  the  deposited  layer  of 
the  reagent. 

Low  has  proposed  the  following  test  for  the  yellow  azo- color : 
A  few  cubic  centimeters  of  the  filtered  fat  are  mixed  in  a  large 
test-tube  with  an  equal  volume  of  a  mixture  of  one  part  strong 
sulfuric  acid  and  four  parts  glacial  acetic  acid.  The  contents 
of  the  tube  are  then  heated  almost  to  boiling  and  thoroughly 
mixed  by  violently  agitating  the  bottom  of  the  tube.  When  now 
allowed  to  stand  and  separate,  the  lower  layer  of  mixed  acids 
will  be  strongly  colored  wine-red  if  the  azo-color  be  present. 
Pure  butter-fat  imparts  no  color  to  the  acids,  or,  at  most,  only 
a  faint  brownish  tinge. 

For  turmeric  and  annatto  mixtures,  Martin's  test  will 
usually  be  satisfactory:  2  c.c.  carbon  disulfid  are  mixed  with 
15  c.c.  of  alcohol,  by  adding  small  portions  of  the  disulfid 
to  the  alcohol  and  shaking  gently;  5  grams  of  the  butter- 
fat  are  added  to  this  mixture  in  a  test-tube  and  shaken.  The 
disulfid  falls  to  the  bottom  of  the  tube,  carrying  with  it  the 
fatty  matter,  while  any  artificial  coloring-matter  remains  in 
the  alcohol.  The  separation  takes  place  in  from  one  to  three 
minutes.  If  the  amount  of  the  coloring-matter  is  small,  more 
of  the  fat  may  be  used.  If  the  alcohohc  solution  be  evaporated 
to  dryness  and  the  residue  treated  with  concentrated  sulfuric 
acid,  annatto  will  be  indicated  by  the  production  of  a  greenish- 
blue  color.  With  many  samples  of  oleomargarin,  a  pink  tint 
will  be  produced,  which  indicates  an  azo-color. 

Palm  oil  is  sometimes  used  as  a  coloring  agent  in  butter- 
substitutes.     Crampton  &  Simons^^  have  found  that  two  tests 


BUTTER  239 

devised  for  detection  of  rosin-oil  can  be  satisfactorily  adapted 
to  detection  of  palm  oil.  Success  depends  on  several  points. 
The  sample  must  be  kept  in  a  cool  dark  place  until  used,  filtered 
at  a  temperature  not  above  70°,  the  heating  as  brief  as  possible, 
and  promptly  tested.     The  reagents  must  be  pure  and  colorless. 

Halphen  method.  100  c.c.  of  the  filtered  fat  are  dissolved  in 
300  c.c.  petroleum  spirit  and  shaken  out  with  50  c.c.  of  potas- 
sium hydroxid  solution  (0.5  per  cent  of  hydroxid).  The  water 
is  drawn  off,  made  distinctly  acid  with  hydrochloric  acid,  and 
shaken  out  with  10  c.c.  of  carbon  tetrachlorid.  This  solution 
is  drawn  off,  and  part  of  it  tested  by  adding  to  it  2  c.c.  of  a  mix- 
ture of  I  part  crystallized  phenol  in  2  parts  carbon  tetrachlorid. 
To  this  add  5  drops  of  hydrobromic  acid  (sp.  gr.  1.19).  The 
test  is  best  performed  in  a  porcelain  basin  and  the  contents 
mixed  by  agitating  gently.  Palm  oil  gives  almost  immediately 
a  bluish-green  liquid. 

Liebermann-Storch  method.  10  c.c.  of  the  filtered  fat  are 
shaken  with  an  equal  volume  of  acetic  anhydrid,  one  drop  of 
sulfuric  acid  (sp.  gr.  1.53)  is  added  and  the  mixture  shaken 
for  'a  few  seconds.  If  palm  oil  be  present,  the  heavier  layer 
separating  will  be  blue  with  a  tint  of  green. 

For  detection  of  yolk  of  egg,  which  has  been  proposed  as  a 
color  for  oleomargarin,  see  under  "  Egg  Substitutes." 

Preservatives. — The  preservatives  used  in  milk  may  be  found 
in  limited  amount  in  butter,  but  a  mixture  of  boric  acid  and 
borax  is  often  added  as  a  substitute  for  salt.  It  will  be  detected 
by  the  method  given  on  page  82  in  the  water  obtained  by  melt- 
ing the  butter  and  allowing  the  mass  to  settle. 

Glucose  is  sometimes  used  as  a  preservative,  especially  in 
butter  intended  for  export  to  tropical  countries.  Crampton 
found  as  much  as  10  per  cent,  in  a  sample  of  highly  colored 
butter  intended  for  exportation  to  Guadeloupe.  For  the  de- 
tection of  glucose  the  phenylhydrazin  test  might  be  used.  For 
det,ermination    Crampton    used    the    following    method :     10 


240  FOOD   ANALYSIS 

grams  of  the  sample  were  washed  with  successive  portions  of 
convenient  bulk,  the  solution  made  up  to  250  ex.,  and  an  aliquot 
portion  determined,  as  given  on  page  113.  The  solution  may 
also  be  clarified  by  alumina-cream  or  acid  mercuric  nitrate  and 
examined  in  the  polarimeter. 

Geisler  found  paraffin  in  oleomargarin ;  his  observation  has 
been  confirmed  by  several  other  chemists.  Geisler  uses  the 
specific  gravity  of  the  rendered  fat  as  a  sorting  test,  making 
special  examination  only  of  samples  that  show  below  0.9018 
at  ^j^.  Microscopic  examination  under  polarized  light,  with 
and  without  selenite,  will  often  show  amorphous  masses  of 
paraffin  mixed  with  the  crystals  of  fat.  To  isolate  the  paraffin, 
Geisler  saponifies  2.5  grams  of  the  fat  with  20  c.c.  of  alcohol 
and  I  gram  of  potassium  hydroxid,  and  dilutes  the  liquid  with 
an  equal  bulk  of  water.  By  alternately  heating  and  cooling 
the  liquid  much  of  the  unsaponifiable  matter  may  be  collected. 
It  is  also  possible  to  isolate  it  by  the  process  given  on  page  159, 
or  by  destroying  the  fat  by  strong  sulfuric  acid.  It  must  be 
borne  in  mind  that  most  fats  contain  notable  amounts  of  un- 
saponifiable matter,  and  hence  the  material  must  be  identified  as 
paraffin. 

CHEESE 

Cheese  is  the  curd  of  milk  which  has  been  separated  from 
it,  pressed,  and  undergone  some  fermentation.  The  precipita- 
tion is  produced  either  by  allowing  the  milk  to  become  sour 
— when  the  lactic  acid  is  the  agent — or  by  rennet.  The  first- 
named  method  is  mainly  applied  to  the  manufacture  of  so- 
called  Dutch  or  sour-milk  cheese,  green  Swiss  cheese,  and 
cottage  cheese.  More  commonly  cheese  is  obtained  by  means 
of  rennet  derived  from  the  fourth  stomach  of  the  calf.  The 
action  is  due  to  an  enzym  which  acts  directly  on  the  proteids 
and  does  not  produce  its  effect  through  the  intervention  of 
acids.     The    curd    (cheese)    undergoes,    by   keeping,    various 


CHEESE  241 

decompositions,  some  essentially  putrefactive,  and  due  to  the 
action  of  microbes.  The  decomposition  of  the  cheese  is  termed 
**  ripening." 

In  the  sour  milk  cheeses,  ripening  is  restricted  intention- 
ally, since  there  is  liability  to  an  irregular  and  miscellaneous 
bacterial  growth  by  which  the  fermentations  may  be  carried 
too  far,  undesirable  and  even  harmful  products  being  formed. 
Such  cheeses  are  intended  for  prompt  use. 

Cheese  contains  no  casein,  if  by  this  term  is  meant  the  proteid 
as  it  exists  in  milk,  or  when  precipitated  from  milk  by  acids. 
When  milk  is  coagulated  by  rennet,  only  a  part  of  the  proteids 
enter  into  the  curd;  true  casein  contains  about  15.7  per  cent, 
of  nitrogen,  but  the  proteid  matter  of  cheese  contains  about 
14.3  per  cent.  Under  the  process  of  ripening  this  is  further 
decomposed,  amido-  and  ammonium  compounds,  peptones 
and  albumoses,  being  formed. 

The  following  figures,  obtained  by  Van  Slyke,  will  serve 
to  give  some  idea  of  the  extent  to  which  the  curd  is  changed 
in  ripening.  The  figures  represent  average  percentage  on  the 
total  nitrogen.     The  cheese  was  an  American  cheddar: 

Green  Cheese.  After  Five  Months. 

Soluble  nitrogen  compounds, 4.23  35-52 

"      amido  "  none  11.66 

"      ammonium     "  none  2.92 

Van  Slyke' s  experiments  seem  also  to  indicate  that  the  cheese 
ripened  more  rapidly  when  the  curd  was  precipitated  by  a 
larger  quantity  of  rennet  and,  especially,  that  cheese  rich  in 
fat  ripened  more  rapidly  than  skim-milk  cheese. 

In  addition  to  the  fat  and  nitrogenous  compounds  just  men- 
tioned, cheese  may  contain  a  small  amount  of  milk-sugar  and 
of  lactic  and  other  organic  acids.  There  is  present  also  a  cer- 
tain proportion  of  mineral  matter,  alkaline  and  earthy  phos- 
phates, along  with  any  salt  that  has  been  added.  Traces  of 
nitrates  have  been  found. 
22 


242  FOOD  ANALYSIS 

Skimmed  milk  is  not  infrequently  used  for  the  production 
of  cheese.  Partially-skimmed  milk  is  used  in  the  preparation 
of  certain  Dutch  cheeses.  Foreign  fats,  such  as  are  used  in 
the  manufacture  of  oleomargarin,  are  sometimes  incorporated, 
the  article  being  known  as  "filled  cheese." 

The  ash  of  cheese  consists  largely  of  calcium  phosphate  and 
salt.  Mariani  &  Tasselli  have  estimated  the  total  ash, 
chlorin,  calcium,  and  phosphoric  acid  in  15  samples  of 
cheese.  The  amounts  of  salts  (calculated  from  the  chlorin)  de- 
pend on  the  mode  of  salting.  The  proportion  of  phosphoric 
oxid  was  always  greater  than  that  necessary  to  form  trical- 
cium  phosphate,  ranging  from  1.07  and  1.08  equivalents  of 
phosphoric  anhydrid  to  calcium  oxid  in  cheese  made  from 
sour  milk  to  1.56  to  i  in  Gorgonzola,  1.67  to  i  in  skim-milk 
cheese,  and  1.75  to  i  in  Edam  cheese.  The  largest  quanti- 
ties of  calcium  and  phosphoric  oxid  were  found  in  sheep 's- 
milk  cheese  and  in  cheese  made  from  sour  milk,  whence  it 
follows  that  acidity  does  not  prevent  the  precipitation  of  cal- 
cium phosphate  in  the  curds.  The  excess  of  phosphoric  oxid 
obtained  was  attributed  to  acid  phosphates. 

The  salt  in  cheese  usually  ranges  between  i  and  4  per  cent. 

Analytic  Methods. — The  analytic  points  usually  deter- 
mined in  regard  to  cheese  are  water,  fat,  casein,  ash,  the  pres- 
ence of  fats  other  than  butter-fat,  and  coloring-matters. 

In  addition  to  this,  especially  in  comparing  the  qualities  of 
genuine  cheeses,  the  proportion  of  proteic,  amidic,  and  ammo- 
niacal  nitrogen  is  of  value. 

Care  should  be  taken  to  select  for  analysis  a  sample  which 
represents  the  average  composition  of  the  entire  cheese. 

The  following  methods  for  the  determination  of  water,  fat, 
ash,  total  nitrogen,  and  acidity  have  been  adopted  by  the  A.  O. 
A.  C: 

Sampling. — When  the  cheese  can  be  cut,  a  narrow  wedge- 
shaped  segment,  reaching  from  the  outer  edge  to  the  center 


CHEESE  243 

of  the  cheese,  is  taken.  This  is  to  be  cut  into  strips  and  passed 
through  a  sausage-grinding  machine  three  times.  When  the 
cheese  cannot  be  cut,  samples  are  taken  by  a  cheese  trier.  If 
only  one  plug  can  be  obtained,  this  should  be  perpendicular 
to  the  surface,  at  a  point  one-third  of  the  distance  from  the  edge 
to  the  center  of  the  cheese.  The  plug  should  reach  entirely 
through,  or  only  half-way  through,  the  cheese.  When  possible, 
draw  three  plugs — one  from  the  center,  one  from  a  point  near 
the  outer  edge,  and  one  from  a  point  half-way  between  the 
other  two.  For  inspection  purposes,  the  rind  may  be  rejected; 
but  for  investigations  requiring  the  absolute  amount  of  fat  in 
the  cheese,  the  rind  is  included  in  the  sample.  It  is  preferable 
to  grind  the  plugs  in  a  sausage  machine,  but  when  this  is  not 
done,  they  should  be  cut  very  fine  and  carefully  mixed. 

Water. — Between  2  and  5  grams  of  the  sample  should  be 
placed  in  a  weighed  platinum  or  porcelain  dish  which  con- 
tains a  small  amount  of  material,  such  as  freshly  ignited  asbestos 
or  sand,  to  absorb  the  fat  that  may  run  out.  This  is  then  heated 
in  a  water-oven  for  10  hours  and  weighed;  the  loss  in  weight 
is  considered  as  water.  If  preferred,  the  dish  may  be  placed 
in  a  desiccator  over  concentrated  sulfuric  acid  and  dried  to  con- 
stant weight,  but  this  may  require  many  days.  The  acid 
should  be  renewed  when  the  cheese  has  become  nearly  dry. 

Fat. — The  extraction-tube  described  on  page  200  is  prepared 
as  follows:  Cover  the  perforations  in  the  bottom  of  the  tube 
with  asbestos,  and  on  this  place  a  mixture  containing  equal 
parts  of  anhydrous  copper  sulfate  and  pure  dry  sand  to  the 
depth  of  about  5  cm.,  packing  loosely,  and  cover  the  upper 
surface  with  a  film  of  asbestos.  On  this  are  placed  from  2  to  5 
grams  of  the  sample,  the  mass  extracted  for  5  hours  with  anhy- 
drous ether,  then  removed  and  ground  to  fine  powder  with  pure 
sand  in  a  mortar.  The  mixture  is  placed  in  the  extraction 
tube,  the  mortar  washed  free  from  all  matters  with  ether,  the 
washings  being  added  to  the  tube,  and  the  extraction  is  con- 


244  FOOD   ANALYSIS 

tinued  for  lo  hours.  The  fat  so  obtained  is  dried  at  ioo°  to 
constant  weight. 

Here,  as  in  most  extractions,  carbon  tetrachlorid  can  be 
substituted  for  ether,  but  the  resuks  obtained  are  not  neces- 
sarily equivalent. 

Total  Nitrogen. — This  is  determined  by  the  Kjeldahl-Gun- 
ning  method,  using  2  grams  of  the  sample.  The  percentage, 
multiplied  by  6.38,  gives  the  nitrogen  compounds. 

Ash. — The  dry  residue  from  the  water  determination  may 
be  taken  for  the  ash.  If  the  cheese  be  rich,  the  asbestos  will 
be  saturated  therewith.  This  mass  may  be  ignited  carefully, 
and  the  fat  allowed  to  burn  off,  the  asbestos  acting  as  a  wick. 
No  extra  heating  should  be  applied  during  the  operation,  as 
there  is  danger  of  spurting.  When  the  flame  has  died  out, 
the  burning  may  be  completed  in  a  muffle  at  low  redness. 
When  desired,  the  salt  may  be  determined  in  the  ash  by  titra- 
tion with  silver  nitrate  and  potassium  chromate. 

Provisional  Method  for  the  Determination  of  the  Acidity  in 
Cheese. — Water  at  a  temperature  of  40°  is  added  to  10  grams 
of  finely  divided  cheese  until  the  volume  equals  105  c.c,  agitated 
vigorously,  and  filtered.  Portions  of  25  c.c.  of  the  filtrate 
corresponding  to  2.5  grams  of  the  cheese  are  titrated  with  deci- 
normal  solution  of  sodium  hydroxid,  using  phenol-phthalein 
as  indicator.     The  amount  of  acid  is  expressed  as  lactic  acid. 

The  above  processes  may  be  advantageously  modified  in 
some  respects.  The  determination  of  water  may  be  made  by 
the  extraction  of  the  cheese  with  alcohol  and  ether  and  drying 
of  the  alcohol-ether  extract  and  fat-free  solids  separately. 
Blyth  recommends  this  method  as  more  accurate  and  less 
tedious  than  the  direct  drying.  In  the  determination  of  ash 
it  will  be  better  to  extract  the  charred  mass  with  water  and 
proceed  as  described  in  the  determination  of  the  ash  of  milk. 

The  fat  extracted  by  ether  may  be  examined  for  other  than 
butter-fat  by  the  distillation  method  in  the  usual  way.     When 


CHEESE  245 

the  composition  of  the  fat  is  alone  desired,  it  may  often  be  ex- 
tracted by  simple  methods.  Pearmain  &  Moor  recommend 
that  50  grams  be  chopped  fine  and  tied  up  in  a  muslin  bag, 
which  is  placed  in  a  water-bath.  When  the  water  is  heated,  the 
fat  will  generally  run  out  clear.  If  not  clear,  it  can  be  filtered 
through  paper. 

Henzold  suggests  the  following :  300  grams  of  the  powdered 
cheese  are  agitated  in  a  wide-neck  flask  with  700  c.c.  of  5  per 
cent,  solution  of  potassium  hydroxid  previously  warmed  to  20°. 
In  about  10  minutes  the  cheese  dissolves,  the  fat  floats,  and  by 
cautious  shaking  may  be  collected  in  lumps.  The  hquid  is 
diluted,  the  fat  removed,  washed  in  very  cold  water,  kneaded 
as  dry  as  possible,  melted,  and  filtered.  It  is  claimed  that  the 
fat  is  not  altered  in  composition  by  the  process. 

The  fat  of  cheese  may  be  estimated  by  the  centrifugal  method, 
as  follows: 

About  3  grams  of  the  mixed  cheese  in  small  fragments  are 
weighed  and  transferred  to  the  bottle,  the  last  portions  being 
washed  in  with  the  acid  of  water.  A  few  drops  of  ammonium 
hydroxid  are  added,  and  sufficient  water  to  make  the  liquid 
about  15  c.c.  The  liquid  is  warmed  with  occasional  shaking 
until  the  cheese  is  well  disintegrated,  and  then  treated  as  a 
sample  of  milk.  The  percentage  of  fat  is  found  by  multiply- 
ing the  percentage  reading  by  15.45  and  dividing  by  the  num- 
ber of  grams  of  cheese  taken  for  analysis. 

Chattaway,  Pearmain,  &  Moor  use  the  following  modifica- 
tion: 2  grams  of  the  cheese  are  placed  in  a  small  dish  and 
heated  on  the  water-bath  with  30  c.c.  of  concentrated  hydro- 
chloric acid  until  a  dark,  purplish-colored  solution  is  produced. 
The  mixture  is  now  poured  into  the  test  bottle,  portions  of 
solution  remaining  in  the  dish  rinsed  with  the  hydrochloric  acid 
fusel-oil  mixture  into  the  bottle,  and,  finally,  enough  strong  hot 
acid  added  to  fill  the  bottle  up  to  the  mark.  It  is  then  whirled 
for  about  a  minute.     The  difficulty  in  this  method  is  to  get  all 


246  FOOD  ANALYSIS 

the  fat  into  the  bottle.  It  is  best  to  weigh  the  cheese  in  the 
bottle. 

Bondzynksi  applies  the  Werner-Schmid  method  to  the  de- 
termination of  fat  in  cheese,  as  follows:  A  weighed  quantity 
of  the  finely- shredded  cheese  is  placed  in  the  tube  and  decom- 
posed with  20  c.c.  hydrochloric  acid  of  specific  gravity  i.i, 
containing  about  19  per  cent,  true  acid.  On  cautiously  warm- 
ing over  wire  gauze,  the  melted  fat  rises  to  the  surface.  After 
cooling,  30  c.c.  of  ether  are  added  and  the  tube  warmed  very 
gently  until  the  acid  and  ethereal  solution  of  fat  separate  sharply. 
Centrifugal  force  helps  this,  but  is  not  essential.  After  the  vol- 
ume of  ether  has  been  read  off,  20  c.c.  are  pipetted  off  into  a 
weighed  Erlenmeyer  flask.  From  this,  the  quantity  of  fat  in 
the  entire  solution  may  be  calculated. 

Lactose. — This  may  be  estimated  by  boiling  the  finely  di- 
vided cheese  with  water,  filtering,  and  determining  the  reduc- 
ing power  of  the  filtrate  on  Fehling's  solution. 

Determination  of  Proteid  Nitrogen  (Stutzer's  Method). — 0.7 
to  0.8  gram  of  the  cheese  are  placed  in  a  beaker,  heated  to 
boiling,  2  or  3  c.c.  of  saturated  alum  solution  added  to  decom- 
pose alkaline  phosphate,  then  copper  hydroxid  mixture  (see 
page  37)  containing  about  0.5  gram  of  the  hydroxid,  and  stirred 
in  thoroughly;  when  cold,  the  mass  is  filtered,  washed  with 
cold  water,  and,  without  removing  the  precipitate  from  the  filter, 
the  nitrogen  determined  by  the  Kjeldahl- Gunning  method. 
Before  distillation,  sufficient  potassium  sulfid  solution  must  be 
added  to  precipitate  the  copper. 

Ammonium  Compounds. — About  5  grams  of  cheese  are 
rubbed  up  in  a  mortar  with  water,  transferred  to  a  filter,  and 
washed  with  a  liter  of  cold  water.  The  filtrate  is  concentrated 
by  boiling  (if  alkaline,  it  must  be  neutralized  before  heating), 
barium  carbonate  added,  the  liquid  distilled,  and  the  ammo- 
nium hydroxid  in  the  distillate  estimated  by  titration  with  stan- 
dard acid. 


CHEESE  247 

According  lo  Stutzer,  magnesia  or  magnesium  carbonate 
(the  latter  usually  contains  some  magnesia)  should  not  be  used 
to  free  the  ammonia,  as  some  of  the  amido-compounds  may 
be  decomposed. 

Amido-compounds. — The  nitrogen  as  amido-compounds  is 
estimated  by  subtracting  from  the  figure  for  total  nitrogen  the 
sum  of  the  proteid  and  ammoniacal  nitrogen.  If  nitrates  are 
present,  the  nitrogen  as  such  should  also  be  determined  and 
substracted. 

Van  Ketel  &  Antusch  propose  the  following  methods  for 
estimating  the  nitrogen  compounds: 

Ammonium  Compounds. — The  sample,  powdered  with  the 
addition  of  sand,  is  distilled  wtth  water  and  barium  carbonate, 
and  the  distillate  received  in  a  measured  quantity  of  standard 
sulfuric  acid,  and,  after  boiling,  the  excess  of  acid  is  neutral- 
ized with  standard  sodium  hydroxid,  using  rosolic  acid  as 
indicator. 

Amido-compounds. — These  are  estimated  by  macerating  the 
pawdered  cheese  in  water  for  15  hours  at  the  ordinary  tem- 
perature. After  adding  a  httle  dilute  sulfuric  acid  (i  :  4),  the 
proteids  and  peptones  are  precipitated  by  phosphotungstic 
acid.  The  precipitate  is  filtered  off  and  washed  with  water 
containing  a  little  sulfuric  acid.  The  filtrate  is  made  up  to  a 
definite  bulk,  and  the  nitrogen  is  determined  in  an  aliquot  por- 
tion of  the  liquid  by  the  Kjeldahl- Gunning  process,  allow- 
ance being  made  for  the  nitrogen  existing  as  ammonium. 

Peptones  and  Albumoses. — These  are  determined  jointly  by 
boiling  the  powdered  cheese  (mixed  with  sand  as  before)  with 
water  and  filtering  from  the  undissolved  casein  and  albumin. 
In  an  aliquot  portion  of  the  filtrate  the  peptones  and  albu- 
moses are  precipitated  by  adding  dilute  sulfuric  acid  and 
phosphotungstic  acid.  After  washing  with  acidulated  water 
the  nitrogen  in  the  precipitate  is  determined  by  the  Kjeldahl- 
Gunning  process. 


248  FOOD   ANALYSIS 

The  total  nitrogen  of  the  cheese  is  also  determined,  and  after 
allowing  for  the  nitrogen  existing  as  other  forms,  the  balance 
is  calculated  to  casein. 

Poisonous  Metals. — Lead  chromate  has  been  found  in  the 
rind  of  cheese,  and  finely  divided  lead  in  a  number  of  Cana- 
dian cheeses.  In  England  zinc  sulfate  has  been  employed 
under  the  name  of  cheese  spice  to  prevent  the  heading  and  crack- 
ing. Arsenic  has  also  been  found;  it  may  be  detected  by 
Reinsch's  test.  Lead,  zinc,  and  chromium  may  be  detected 
by  ashing  a  portion  of  the  sample  in  a  porcelain  crucible  and 
proceeding  as  on  page  58. 

ANALYSES  OF  VARIOUS    CHEESES 
(Reports  by  W.  A.  Chattaway,  T.  M.  Pearmain,  and  C.  G.  Moor) 

ReichertMeissl 
Name.  Water.      Ash         Fat.      Number.        N. 

Cheddar, 33.0  4.3  29.5  24.2  4.31 

Gorgonzola, 40.3  5.3  26.1  22.1  4.36 

Dutch, 41.8  6.3  10.6  27.0  5. II 

Gruyere, 28.2  4.7  28.6  30.0  4.93 

Stilton, 19.4  2.6  42.2  29.0  4.73 

Cheshire, 37.8  4.2  31.3  31.6  4.03 

Gloucester, 33.1  5.0  23.5  31.4  4.99 

Camembert, 47.9  4.7  41.9  31.0  3.83 

Parmesan, 32.5  6.2  17. i  28.0  6.86 

Roquefort, 29.6  6.7  30.3  36.8  4.45 

Double  Cream, 57.6  3.4  39.3  31.2  3.14 

Filled  (United  States), 30.6  3.6  27.7  3.0  4.84 

The  common  American  cheese  is  knov^n  as  Cheddar.  Ac- 
cording to  Van  Slyke,  this  has,  when  ripe,  about  the  following 
average  composition: 

Water, -31.50  per  cent. 

Fat, 37.00        " 

Proteids, 26.25       " 

Ash,  sugar,  etc., 5.25       " 

FERMENTED  MILK  PRODUCTS 

The  usual  fermentation  of  milk  is  the  conversion  of  the 
lactose  into  lactic  acid,  but  by  special  methods  other  changes 


FERMENTED   MILL   PRODUCTS  249 

may  be  substituted.  These  modified  fermentations  are  of 
rather  ancient  origin,  and  b^ing  produced  by  mixture  of  organ- 
isms, the  products  are  complex  and  irregular.  The  proteids 
are  more  or  less  changed  into  proteoses  and  peptones. 

Kumiss  is  milk  which  has  undergone  alcoholic  fermentation. 
The  inhabitants  of  the  steppes  of  Russia  prepare  it  from  mares' 
milk.  When  cows'  milk  is  used,  cane-sugar  must  be  added. 
It  is  often  made  by  adding  cane-sugar  and  yeast  to  skim-milk. 

P.  Vieth  gives  the  following  analysis  of  kumiss  at  successive 
stages  of  fermentation: 

KUMISS  FROM  COWS'  MILK 

Onk  One  Three 

One  Day.       Week.      Month.      Months. 

Alcohol, I.I  0.9  i.o  I.I 

Solids, 11.3  8.9  8.6  8.5 

Fat, 1.6  1.4  1.5  1.5 

Casein, 2.0  2.0  1.9  1.7 

Albumin,    0.3  0.2  0.2  o.i 

Sugar, 6.1  3.1  2.2  1.7 

Lactic  acid, 0.2  0.9  1.3  1.9 

Lactoproteid  and  peptone, 0.3  0.5  0.7  0.9 

Soluble  ash. o.i  0.2  0.2  0.2 

Insoluble  ash, 0.4  0.3  0.3  0.3 

The  item  "lactoproteid  and  peptone"  refers  to  the  sub- 
stances precipitated  by  tannin  after  removal  of  the  casein  and 
albumin. 

KUMISS  FROM  MARES'  MILK 

At  the  Nitrogenous     Lactic 

End  of:  Alcohol.  Fat.  Matters.  Aao.  Sugar.       Ash. 

I  day, 2.47  1.08  2.25  0.64  2.21        0.36 

8  days, 2.70  1.13  2.00  1.16  0.69       0.37 

22     **     .2.84  1.27  1.97  1.26  0.51        0.36 

Kejyr. — This  is  usually  made  from  cows'  milk.  It  has  been 
used  in  the  Caucasus  for  centuries.  For  its  preparation  a  pecu- 
liar ferment  is  used,  which  is  contained  in  the  kefyr  grains. 
These  are  first  soaked  in  water,  by  which  they  are  caused  to 
swell  and  are  rendered  more  active,  and  then  added  to  the  milk. 


250  FOOD  ANALYSIS 

If  taken  out  of  the  milk  and  dried,  the  grains  may  be  used 
repeatedly. 

The  following  are  analyses  of  kefyr: 

KoNiG.  Hammarsten. 

Alcohol, 0.75  0.72 

Fat, 1.44  3.08 

Casein, 2.88  2.94 

Albumin, 0.36  0.18 

Hemialbumose, 0.26  0.07 

Peptone. 0.04 

Sugar, 2.41  2.68 

Lactic  Acid, 1.02  0.73 

Ash, 0.68  0.71 

According  to  Konig,  good  kefyr  will  not  contain  more  than 
I  per  cent,  of  lactic  acid. 

Analytic  Methods. — Fixed  solids  and  ash  are  determined 
by  evaporations  of  a  weighed  amount  in  a  platinum  basin  as 
described  on  page  200.  Acidity  is  determined  by  filtration  with 
^-  alkali,  using  phenolphthalein  or  methyl-orange  as  an  indica- 
tor. The  amount  of  acidity  is  expressed  in  terms  of  lactic  acid. 
The  Kjeldahl- Gunning  method  will  give  the  total  nitrogen. 
For  further  examination  of  the  nitrogenous  bodies,  the  methods 
given  on  pages  246  and  247  may  be  applied.  Total  reducing 
sugars  may  be  estimated  as  given  on  page  113.  If  sucrose 
and  common  yeast  have  been  added,  the  fermented  material 
will  be  likely  to  contain  invert- sugar,  with  unchanged  lactose 
and  sucrose,  and  the  method  of  examination  of  sweetened  con- 
densed milk  may  be  applicable.  Fat  can,  probably  in  all  cases, 
be  determined  with  sufficient  accuracy  by  the  L-B.  process. 
If  it  be  desired  to  make  polarimetric  readings,  the  liquid  should 
be  clarified  with  acid  mercuric  nitrate  solution  (page  211),  as 
some  partly  hydrolyzed  proteids  which  have  rotatory  power 
may  not  be  precipitated  by  other  reagents.  The  determination 
of  alcohol  accurately  is  difficult,  as  the  quantity  is  usually  small. 
The  cautious  distillation  of  a  considerable  volume  of  the  ma- 


FERMENTED   MILK   PRODUCTS  25 1 

terial  previously  neutralized  with  a  little  sodium  hydroxid  will 
yield  a  distillate  in  which  alcohol  may  be  determined  by  specific 
gravity. 

Preservatives  are  not  likely  to  be  used,  since  they  would 
interfere  with  the  fermentation,  but  attempts  may  be  made  to 
secure  better  keeping  by  adding  some  preservative  after  the 
fermentation  has  occurred.  In  some  cases,  therefore,  tests 
for  boric  acid,  formaldehyde,  and  salicylic  acid  should  be  made, 
as  these  will  be  most  likely  to  be  used. 


252  FOOD  ANALYSIS 

NON-ALCOHOLIC  BEVERAGES 
TEA 

Tea  is  the  prepared  leaf  of  several  species  of  Thea.  Black 
and  green  tea  are  derived  from  the  same  plant,  the  difference 
being  due  to  the  preparation.  The  quality  of  tea  depends  much 
upon  the  age  of  the  leaf  and  the  time  of  picking.  Figure 
46  shows  the  tea  leaf  (i)  and  the  mate  (Paraguay  tea)  leaf  (2). 

Many  pickings  are  made  in  a 
season,  the  first  being  of  the 
finest  quality. 

Black  tea  is  prepared  by  ex- 
posing the  leaves  to  the  sun  until 
they  have  withered.  They  are 
then  rolled  and  again  set  aside, 
usually  in  the  sun,  covered  with 
a  white  cloth  until  fermentation 
takes  place.  They  are  then  ex- 
posed in  a  thin  layer  until  they 
have  become  quite  dark,  and  are 
finally  dried  by  heat. 
Fig.  46,  Green  tea  undergoes  no  fer- 

mentation. In  Japan,  the  leaves 
are  steamed  until  soft,  rolled,  and  dried;  in  China,  they  are 
heated  in  pans. 

In  addition  to  tannin  and  the  usual  plant  constituents,  tea, 
contains  a  notable  proportion  of  caffein.  In  a  given  variety 
of  tea,  the  proportion  of  caffein  usually,  but  not  always,  bears 
some  relation  to  the  quality,  and  so  does  the  soluble  ash  and 
water- extract. 

Caffein  (thein),  trimethylxanthin,  has  been  found  in  tea, 
coffee,  mate  (Paraguay  tea),  gauarana,  and  kola.  When  slowly 
crystallized  from  its  solution  in  chloroform  or  water,  it  forms 


TEA  253 

light,  silky  flexible  needles.  The  proportion  of  water  found 
by  experiment  is  rather  less  than  one  molecule,  owing  probably 
to  loss  by  efflorescence.  It  becomes  anhydrous  at  100°,  and  if 
the  heating  be  long  continued,  a  little  is  volatilized,  but  it  does 
not  volatilize  with  steam.  It  melts  at  231  to  230°,  and  at  384° 
boils  with  partial  decomposition.  It  is  slightly  soluble  in  cold 
water,  but  dissolves  readily  in  hot,  giving  a  bitter  solution. 
It  is  slightly  soluble  in  alcohol,  less  so  in  absolute  alcohol, 
only  sparingly  in  cold  ether,  nearly  insoluble  in  petroleum 
spirit  and  freely  in  chloroform  and  benzene.  It  is  decom- 
posed by  heating  with  dilute  solution  of  sodium  hydroxid, 
barium  hydroxid,  or  calcium  hydroxid. 

Caffein  responds  to  the  so-called  "murexid"  test.  A 
small  amount  is  dissolved  in  a  few  drops  of  hydrochloric  acid, 
a  little  potassium  chlorate  added,  the  liquid  evaporated  to  dry- 
ness on  the  water-bath,  and  the  residue  exposed  to  the  vapor  of 
ammonium  hydroxid;   a  deep  purple  will  be  produced. 

The  following  analyses  by  Kozai  indicate  the  difference  in 
composition  between  green  and  black  Japan  teas.  The  figures 
represent  percentage  on  the  dry  material: 

Original  Leaves.     Green  Tea.     Black  Tea. 

Crude  fiber, 10.44  10.06  10.07 

"     protein, 37.33  37.43  38.90 

Ether  extract, 6,49  5.52  5.82 

Other  nitrogen-free  extract, 27.86  3^-43  35-39 

Ash, 4.97  4.92  4.93 

Caffein, 3.30  3.20  3.30 

Tannin, 12.91  10.64  4-89 

Water-extract, 50-97  53-74  47-23 

Nitrogen,  total, 5.97  5.90  6.22 

"        of  albuminoid, 4.11  3.94  4. 11 

"        of  caffein, 0.96  0.93  0.96 

"        of  amido-compounds, .  0.91  1.13  1.16 

Indian  teas.     Results  from  a  great  number  of  examinations: 

Moisture, 5.83  to  6.32  per  cent. 

Insoluble  leal, 4712  "  5587  " 

Extract, 37.80  "  40.35 

Tannin 13.04  "  18.87 

Caffein, 1.88  "  3.24  " 

Ash,  total, •. 5.05  "  6.02  " 

"    soluble  in  water, 3.12  "  4.28  " 

"    insoluble  in  acid, 0.12  "  0.30  " 


254 


FOOD  ANALYSIS 


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255 


It  is  probable  that  the  proportion  of  caffein  in  the  above 
analyses  is  slightly  underestimated  as  the  determination  was 
made  by  treating  the  watery  extract  with  magnesia,  evapo- 
rating to  dryness,  and  extracting  with  ether. 

The  tea  leaf  is  ovate-lanceolate  with  short  5tem  not  sharply 
distinguished  from  the  blade.  The  distal  two-thirds  of  the 
leaf  is  marked  by  serrations  with  slightly  curved  spines.  At  the 
insertion  of  these  spines  the  leaf  tissue  is  thickened.  This 
structure  is  wanting  in  young  leaf  buds.     The  venation  is  a 


Fig.  47. — Epidermis  of  Under  Surface  of  Tea-leaf. 
5/>,  stoma;   h,  hair;  m,  cells  containing  chlorophyl.     (X  160.) 


midrib  running  to  the  extreme  end  of  the  leaf  with  frequent 
lateral  nearly  opposite  branchings  anastomosing  near  the  edge 
and  sending  off  secondary  branches  to  the  extreme  edge.  The 
apex  of  the  tea  leaf  is  often  distinctly  notched,  whereas  most 
other  leaves  are  pointed.  The  stomata  and  hairs  are  fairly 
characteristic.     Figure  47  is  from  Moeller's  work.*' 

Adulteration. — The  substitution  of  inferior  grades  of  tea 
for  those  of  finer  aroma  and  strength  is  the  common  adulter- 
ation of  tea.     Other  forms  are:     additions,  such  as  sand,  ex- 


256  FOOD   ANALYSIS 

hausted  leaves,  foreign  leaves,  and  materials  to  increase  astrin- 
gency,  especially  catechu.  Green  tea  is  often  colored  or  "faced" 
with  Prussian  blue,  indigo,  or  turmeric,  and  black  tea  with 
graphite.  Lie  tea  is  an  imitation  made  of  dust  and  sweepings 
of  tea  or  other  leaves  along  with  mineral  matter  of  various 
kinds  and  held  together  by  means^of  starch  or  gum.  It  is 
readily  detected  by  the  addition  of  hot  water,  when  the  mass 
breaks  down  into  the  fragments  of  which  it  is  composed. 

The  following  analyses  of  spurious  teas,  received  from  the 
United  States  consuls  at  Canton  and  Nagasaki  (Japan),  were 
made  by  Battershall''^: 

I.  2.  3.  4. 

Total  ash, 8.62  8.90  7.95  12.58 

Ash  insoluble  in  water, 7.98  6.04  4.95  8.74 

Ash  soluble  in  water, 0.64  1.86  3.00  3.84 

Ash  insoluble  in  acid, 3.92  3.18  1.88  6.60 

Extract, 7.73  14.00  1276  22.10 

Gum, 10.67  7-3°  11.00  11.40 

Insoluble  leaf, 70.60  70-55  67.00  60.10 

Tannin, 3.13  8.01  14.50  15.64 

Caffein, 0.58  none  0.16  0.12 

1.  Partially  exhausted  and  refired  tea  leaves,  known  as  '^Ching 
Suey^'  (clear  water),  which  name  doubtless  has  reference  to  the 
weakness  of  a  beverage  prepared  from  the  article. 

2.  "Lie  tea,"  made  from  Wampan  leaves. 

3.  A  mixture  of  10  per  cent,  green  tea  and  90  per  cent,  "lie 
tea,"   sometimes  sold  as  "Imperial"   or  "Gunpowder"   tea. 

4.  "Scented  caper  tea,"  consisting  of  tea  dust  made  up  into 
little  shot-like  pellets  by  means  of  "Congou  paste"  (i.  e.,  boiled 
rice). 

Analytic  Methods. 

Water. — This  is  determined  as  on  page  27.  A  slight  amount 
of  caffein  may  be  lost  in  the  drying  and  counted  as  water,  but 
the  error  is  negligible. 

Ash. — Soluble  ash  and  alkalinity  of  soluble  ash.     (See  page 

39)- 


TEA  257 

Extract. — 2  grams  of  the  finely  powdered  tea  are  boiled  for 
an  hour  in  a  flask  provided  with  a  reflux  condenser.  The  liquid 
is  decanted  and  the  residue  boiled  for  a  short  time  with  suc- 
cessive portions  of  50  c.c.  of  water  until  this  is  no  longer  colored. 
The  solutions  are  mixed,  heated,  filtered  through  a  tared  filter, 
to  which  the  insoluble  leaf  is  also  transferred.  After  washing 
with  boiling  water,  the  filter  and  contents  are  dried  to  constant 
weight.  The  extract  is  determined  by  difference,  or,  if  desired, 
the  filtrate  is  made  up  to  a  definite  volume,  and  an  aliquot  por- 
tion evaporated  and  dried  at  100°  and  weighed. 

Nitrogen. — Total  and  albuminoid  nitrogen  is  determined  by 
the  methods  described  on  pages  33  and  37. 

Cafjein. — This  is  best  determined  by  Allen's  method:  6 
grams  of  the  finely  powdered  tea  and  600  c.c.  of  water  are  boiled 
under  a  reflux  condenser  for  six  or  eight  hours;  4  grams  of  lead 
acetate  in  powder  are  then  added  and  the  liquid  again  boiled 
for  ten  minutes.  If,  on  removing  the  source  of  heat,  the  pre- 
cipitate does  not  curdle  and  settle  readily,  leaving  the  liquid 
colorless  or  nearly  so,  a  further  addition  of  lead  acetate  must 
be  made  and  the  boiling  repeated.  When  clarification  is  ef- 
fected, the  liquid  is  passed  through  a  dry  filter,  500  c.c.  of  the 
filtrate  (5  grams  of  the  tea)  are  evaporated  to  about  50  c.c,  and 
a  little  disodium  hydrogen  phosphate  is  added  to  precipitate 
the  remaining  lead.  The  liquid  is  filtered,  the  precipitate 
washed,  and  the  filtrate  further  concentrated  to  about  40  c.c, 
when  the  caffein  is  extracted  by  at  least  four  agitations  with 
chloroform.  The  separated  choroform  solutions  are  mixed, 
and  distilled  in  a  tared  flask  immersed  in  boiling  water.  While 
the  flask  is  still  hot  the  last  traces  of  chloroform  are  removed 
by  a  current  of  air,  and  the  residual  alkaloid  is  weighed. 

Determinations  of  caffein  based  upon  the  treatment  of  the 
leaves  with  boiling  lime  water  or  alkali  are  valueless,  as  is  also 
the  process  of  Paul  &  Cownley,  in  which  the  leaves  are  mixed 
with  magnesia,  dried  and  exhausted  by  alcohol. 
23 


258  FOOD   ANALYSIS 

The  following  volumetric  method,  due  to  Gomberg,  has  been 
reported  upon  favorably  by  Ladd: 

A  weighed  quantity  of  the  tea  is  boiled  with  water  as  above, 
the  solution  made  up  to  a  known  volume,  and  filtered.  An 
aliquot  portion  of  the  filtrate  is  treated  with  lead  subacetate 
so  long  as  a  precipitate  is  formed.  After  standing,  the  pre- 
cipitate is  filtered  off,  the  excess  of  lead  carefully  removed  by 
hydrogen  sulfid,  the  filtrate  from  the  lead  sulfid  boiled  to  re- 
move hydrogen  sulfid,  and  divided  into  two  equal  parts.  One 
portion  is  acidified  with  sulfuric  or  hydrochloric  acid  and  ex- 
cess of  decinormal  iodin  solution  added;  after  standing  5  to  10 
minutes  is  is  filtered  and  the  filtrate  titrated  with  decinormal 
thiosulfate  solution.  If  in  the  other  portion  potassium  iodid- 
iodin  solution  (page  26)  produces  a  precipitate,  a  correction  is 
necessary,  i  c.c.  of  decinormal  thiosulfate  corresponds  to 
0.00458  gram  of  caffein. 

Facing. — The  coloring-matter  used  in  facing  is  usually  present 
in  minute  amount,  and  is  best  detected  by  the  microscope,  the 
leaf  being  examined  by  reflected  light.  A  good  plan  is  to  shake 
some  of  the  leaves  with  water,  allow  the  suspended  matter  to 
settle,  and  examine  the  sediment  by  the  microscope  and  chemic- 
ally. Prussian  blue  may  be  distinguished  from  indigo  by  the 
fact  that  the  color  of  the  former  is  discharged  by  addition  of 
sodium  hydroxid.  Indigo  forms  a  deep  blue  solution  with 
sulfuric  acid.  Turmeric  is  detected  as  on  page  73.  Graphite 
may  be  detected  by  examination  under  the  microscope. 

Added  Mineral  Matter. — Any  considerable  addition  of 
mineral  matter  will  be  shown  by  the  increased  proportion  of 
ash,  which  usually  ranges  from  5  to  6.5  per  cent.,  and  only 
in  exceptional  cases  rises  to  7.5  per  cent.  Magnetic  iron  oxid 
and  particles  of  iron  have  been  found  in  tea,  and  may  be  readily 
separated  from  it  by  the  magnet.  Sand  and  powdered  brick 
have  also  been  found.     The  former  may  be  accidental. 

Exhausted    Tea   Leaves. — The   detection   of   admixture    of 


TEA  259 

moderate  proportion  of  added  tea  leaves  is  difficult.  Con- 
siderable addition  will  be  indicated  by  the  decreased  propor- 
tion of  extract  and  caffein,  and  especially  of  soluble  ash  and  its 
alkalinity.  The  soluble  ash  of  pure  tea  is  from  2.5  to  4  per  cent., 
and  is  usually  over  3  per  cent.,  v^hereas  that  of  exhausted  tea 
is  generally  not  over  0.8  per  cent.  The  alkalinity  of  the  soluble 
ash  expressed  as  potassium  oxid  is  from  1.25  to  2  per  cent,  (cal- 
culated on  the  dry  tea).  In  exhausted  tea  the  alkalinity  is 
likely  to  be  less  than  0.3  per  cent. 

The  soluble  ash  is  best  calculated  to  percentage  of  total  ash. 
The  interference  of  sand  may  be  eliminated  by  calculating  the 
proportion  of  ash  soluble  in  water  to  that  soluble  in  acid. 
Wigner  obtained  the  following  average  results  from  the  ex- 
amination of  67  samples  of  tea: 

Siliceous  matter, 7.96  per  cent. 

Soluble  in  acid, 37-54    "      " 

"       "water, 54.50    "      " 

Alkalinity  of  soluble  ash, 25.09    "      " 

Excluding  the  portion  insoluble  in  acid,  the  figures  become: 

Soluble  in  water, 59-2 1  per  cent. 

Alkalinity  of  soluble  ash, 27,26    "      " 

If  the  soluble  ash  is  less  than  40  per  cent,  of  the  total  ash  or 
less  than  45  per  cent,  excluding  siliceous  matter,  adulteration 
with  exhausted  leaves  may  be  suspected. 

The  minimum  proportion  of  extract  yielded  by  pure  tea  is,  ac- 
cording to  the  standard  fixed  by  the  Society  of  Public  Analysts 
in  1874,  not  less  than  30  per  cent.  The  proportion  usually 
found  much  exceeds  this  figure,  but  congou  may  contain  less. 
The  proportion  of  caffein  found  by  different  observers  ranges 
from  1.8  to  4  per  cent.,  the  lower  proportions  being  found  in 
Japan  teas. 

Exhausted  leaves  have  in  some  instances  been  found  to  be 
partly  unrolled  or  much  frayed  and  broken,  and  more  posi- 


26o  FOOD   ANALYSIS 

tive  indications  might  be  had  by  the  examination  of  selected 
leaves  of  suspicious  appearance. 

Foreign  Astringents. — Catechu  is  sometimes  added,  espe- 
cially to  ''lie"  or  ''caper"  tea,  or  to  mask  the  presence  of  ex- 
hausted leaves.  It  may  be  detected  by  Hager's  test:  About 
a  gram  of  the  sample  is  boiled  with  water,  the  extract  treated 
with  excess  of  lead  monoxid,  and  filtered.  A  solution  of  silver 
nitrate  is  added  to  clear  the  filtrate;  in  the  presence  of  catechu, 
a  yellow  flocculent  precipitate,  which  rapidly  becomes  dark, 
is  formed.  Pure  tea  gives  only  a  slight  grayish  precipitate  of 
silver.  Allen  recommends  the  following  process,  which  should 
be  applied  to  the  suspected  tea,  side  by  side  with  a  genuine  sam- 
ple: I  gram  of  the  pure  tea,  and  an  equal  weight  of  the  sus- 
pected sample,  are  infused  in  separate  portions  of  loo  c.c.  each 
of  boiling  water,  and  the  strained  liquid  precipitated  while 
boiling  with  a  slight  excess  of  neutral  lead  acetate.  20  c.c. 
of  the  filtrate  from  the  pure  tea  (which  should  be  colorless), 
when  cautiously  heated  and  treated  with  a  few  drops  of  sil- 
ver nitrate  solution,  avoiding  excess,  gives  only  a  very  slight 
grayish  cloud  or  precipitate  of  reduced  silver;  but  the  same  tea 
containing  2  per  cent,  of  added  catechu  gives  a  copious  brown- 
ish precipitate,  the  liquid  acquiring  a  distinctly  yellowish  tinge. 
With  a  somewhat  larger  proportion  of  catechu,  the  filtrate  from 
the  lead  precipitate  gives  a  bright  green  color  on  adding  one 
drop  of  dilute  ferric  chlorid,  while  the  solution  from  pure  tea 
gives  only  a  slight  reddish  color,  due  to  the  presence  of  acetate. 
On  allowing  the  liquid  to  stand,  the  adulterated  tea  gives  a  pre- 
cipitate of  a  grayish  or  olive-green  color,  the  pure  tea  under- 
going no  change. 

Foreign  Leaves. — A  small  proportion  of  foreign  leaves,  such 
as  those  of  the  rose,  jasmine,  and  orange,  are  sometimes  added 
to  impart  bouquet,  but  these  are  usually  removed  before  pack- 
ing. Other  foreign  leaves,  especially  the  sloe,  willow,  elder, 
Chloranthus    inconspicuus,    Camellia    sasanqua,    and    Eurya 


TEA  261 

chinensis,  have  been  added  in  considerable  quantity,  but  the 
practice,  so  far  as  concerns  the  tea  shipped  to  the  United  States, 
seems  to  be  less  common  than  formerly.  The  detection  of 
such  additions  is  best  made  by  the  appearance  of  the  leaf  and 
the  microscopic  examination,  but  a  few  chemical  tests  have  been 
proposed  v^hich  may  be  of  some  assistance.  Blyth  proposes 
to  utilize  the  presence  of  manganese,  which  is  a  constant  con- 
stituent of  the  ash  of  tea.  The  suspected  leaf  is  ashed  and  the 
ash  treated  on  fused  platinum  foil  with  potassium  nitrate  and 
carbonate.  The  distinct  green  color  due  to  a  manganate  is 
readily  recognized.  Allen  has  applied  the  test  to  various 
leaves  and  found  manganese  to  be  present  in  the  following: 
Species  of  Thea  (tea),  Camellia  sasanqua,  C.  japonicay  coffee, 
beech,  blackberry,  and  sycamore.  Manganese  was  absent 
from  the  leaves  of  the  hawthorn,  ash,  raspberry,  cherry,  plum, 
and  rose,  and  only  faint  traces  were  detected  in  the  leaves  of  the 
Ilex  Paraguay ensis J  elm,  birch,  lime,  sloe,  elder,  willow  herb, 
and  willow.  Blyth  has  also  proposed  the  following  test,  de- 
pending upon  the  isolation  of  caffein  and  recognition  by  its 
crystalline  form  under  the  microscope:  The  leaf  or  fragment 
is  boiled  for  a  minute  in  a  watch-glass  with  a  very  little  water, 
an  equal  bulk  of  calcined  magnesia  is  added,  and  the  whole 
heated  to  boiling  and  rapidly  evaporated  to  a  large-sized  drop. 
This  drop  is  transferred  to  a  subliming  cell,  and  if,  after  heating 
to  about  110°,  no  crystalline  sublimate  of  caffein  is  obtained, 
the  leaf  cannot  be  a  tea  leaf.  If,  however,  a  sublimate  of  caf- 
fein is  obtained,  it  is  not  conclusive  evidence,  since  other  plants 
contain  the  alkaloid. 

More  satisfactory  results  are  obtained  by  the  examination 
of  the  shape  and  venation  of  the  leaf.  The  sample  should  be 
softened  by  soaking  in  hot  water,  carefully  unrolled,  trans- 
ferred to  a  microscope  slide,  and  examined  with  a  hand  lens. 
Such  examination  will  usually  be  sufficient,  but  in  doubtful 
cases  it  may  be  necessary  to  use  higher  powers. 


262  FOOD  ANALYSIS 

COFFEE 

Coffee  is  the  seed  of  species  of  Cojfea,  cultivated  in  sub- 
tropical climates.  The  fruit  usually  consists  of  two  seeds 
surrounded  by  a  pulp,  which  is  removed  by  fermenting  and 
washing.  The  membranous  pericarp  removed  by  machinery 
is  sometimes  roasted  and  used  as  a  substitute  for  coffee. 

The  following  are  the  more  important  constituents  of  raw 
coffee:  An  essential  oil,  fat,  caffetannates,  caffein,  and  caf- 
fearin.  The  essential  oil  has  been  little  studied.  The  fat  of 
coffee  is  soluble  in  alcohol,  but  its  composition  is  not  yet  clearly 
ascertained. 

Caffetannic  acid  is  crystalline,  astringent,  soluble  in  water, 
less  soluble  in  alcohol,  and  very  sparingly  in  ether.  It  gives 
a  dark  green  coloration  with  ferric  chlorid,  and  does  not  pre- 
cipitate gelatin. 

Coffee  contains  a  fairly  constant  proportion  of  caffein  (see 
page  263).  According  to  Paladino,  there  is  also  present  a  nar- 
cotic alkaloid,  which  he  calls  caffearin.  Paladino's  results 
seem  to  be  corroborated  by  those  of  Forster  &  Riechelmann, 
who  found  an  alkaloid  distinguished  from  caffein  by  the  fol- 
lowing characteristics:  failure  to  respond  to  the  murexid 
test,  precipitability  by  picric  acid,  and  insolubility  in  chloroform. 

Roasted  coffee  contains  a  small  amount  of  sugar,  which, 
according  to  Spencer,  consists  largely  of  sucrose.  It  appears 
to  be  absent  from  raw  coffee  and  is  derived  from  the  decom- 
position of  the  glucosids  (tannins). 

The  aroma  of  roasted  coffee  is  due  to  cafjeol,  which  may  be 
separated  by  distilling  with  water,  agitating  the  distillate  with 
ether,  and  evaporating.  It  is  an  oily  liquid,  slightly  soluble 
in  hot  water,  but  easily  soluble  in  alcohol  and  ether..  By  fu- 
sion with  caustic  soda  it  yields  sodium  salicylate.  The  phy- 
siological effects  of  coffee  are  attributed  to  the  caffeol,  caffein, 
and  caffearin. 

The  roasting  of  coffee  results  in  a  notable  reduction  of  some 


COFFEE  263 

of  the  constituents,  especially  the  caffein,  fat,  and  sugar.  When 
properly  conducted,  the  total  loss  in  weight  amounts  to  from 
12  to  18  per  cent.,  of  which  about  8  per  cent,  represents  moisture. 
Konig  gives  the  following  figures,  calculated  as  percentage  of 
moisture-free  material : 

Raw.  Roasted. 

Soluble  in  water, 30-93  28.36 

Total  nitrogen, 2.21  2.38 

Caffein, 1.33  1.42 

Fat,  14-91  16.14 

Sugar, 3.66  1.35 

Fiber, 31.24  25.07 

Other  nitrogen-free  matter, 34.55  39.84 

Ash, 3.92  3.87 

Coffee  is  sometimes  glazed  with  sugar  before  roasting.  Ac- 
cording to  Konig,  when  so  treated  it  retains  much  more  mois- 
ture. According  to  Hilger  &  Juckenack,  glazed  coffee  requires 
to  be  heated  to  a  much  higher  temperature,  which  results  in 
about  double  the  usual  loss  of  caffein  and  fat. 

R,aw  coffee  is  subject  to  less  adulteration  than  roasted  and 
especially  ground  coffee.  Coffee  beans  dififer  considerably  in 
size  and  quality  according  to  their  origin,  and  the  inferior 
kinds  are  sometimes  so  treated  as  to  give  them  the  appearance 
of  the  better  quahties. 

West  India  coffee  is  for  the  most  part  even-sized,  pale  and 
yellowish,  firrn  and  heavy,  with  fine  aroma,  losing  little  weight 
by  the  roasting  process. 

Brazil  coffee  is  larger,  less  solid,  greenish  or  white,  usually 
styled  by  the  brokers  "low"  or  ''low  middlings." 

Java  coffee  is  smaller,  shghtly  elongated,  pale  in  color,  light 
and  deficient  in  essential  oil. 

Ceylon  coffee  is  of  all  descriptions,  but  the  ordinary  planta- 
tion products  are  even-colored,  slightly  canoe-shaped,  strong 
in  aroma  and  flavor,  heavy,  and  permit  of  adulteration  more 
than  other  kinds. 


264  FOOD   ANALYSIS 

Mocha  coffee  is  usually  considered  the  best,  but  very  little 
reaches  the  United  States.  Porto  Rico  coffee  is  often  called 
Mocha.  The  grains  of  Mocha  coffee  are  small  and  dark 
yellow. 

Java  coffee,  when  new,  is  pale  yellow,  and  is  then  cheaper 
than  when  old  and  brown.  This  color  is  partly  the  effect  of 
curing  as  well  as  the  result  of  age. 

Java  coffee,  being  of  high  price,  has  been  imitated  by  color- 
ing the  cheaper  grades  with  dyes  or  mineral  pigments. 

According  to  Waller,  Java  coffee  is  imitated  by  exposing 
South  American  coffee  to  a  high  moist  heat,  by  which  the  color 
is  changed  from  green  to  brown. 

Raw  coffee  is  heavier  than  water.  Fade  gives  the  specific 
gravity  of  raw  coffee  berries  at  from  1.041  to  1.368.  Dam- 
aged coffee  that  has  been  washed  and  partially  roasted  to  im- 
prove the  color  may  have  a  specific  gravity  less  than  i .  Roasted 
coffee  has  a  specific  gravity  of  from  0.500  to  0.635,  t>ut  samples 
that  have  been  made  to  take  up  much  water  by  steaming  and 
then  coating  with  glycerol  or  sugar  (see  page  263)  may  possess 
a  specific  gravity  appreciably  higher  (0.650  to  0.770).  Implicit 
reliance  should  not  be  placed  on  these  figures,  since  over- 
roasted coffees  may  be  heavier  than  water.  The  specific  gravity 
of  raw  coffee  may  be  determined  by  immersing  the  beans  in 
strong  brine  and  cautiously  adding  water  until  they  remain 
suspended  in  the  liquid.  The  specific  gravity  of  the  liquid  is 
then  determined  as  usual.  In  the  case  of  roasted  coffee  the 
brine  is  replaced  by  petroleum  spirit  to  which  is  gradually  added 
ordinary  petroleum. 

Adulteration  with  exhausted  coffee  beans  is  reported  by 
Roos.  The  samples  examined  yielded  only  i  per  cent,  of  ether 
extract. 

Facing. — The  following  are  reported  to  have  been  used  as 
''facing"  for  coffee.  Scheele's  green,  chrome  yellow,  ochre, 
silesian   blue,    burnt   umber,   Venetian   red,   charcoal,   indigo. 


COFFEE  265 

ultramarine  blue,  clay,  gypsum.  A  blue  color  is  also  said  to 
be  produced  by  shaking  the  beans  with  finely  powdered  iron. 
The  beans  are  sometimes  polished  by  rotating  in  a  cylinder 
with  soapstone. 

The  examination  for  facing  should  be  made  with  the  micro- 
scope, and  also  by  shaking  with  water,  and  examining  the 
sediment,  as  described  under  tea  (page  258).  Artificial  colors 
may  usually  be  detected  by  treating  the  beans  with  strong 
alcohol,  evaporating  to  dryness,  and  testing  the  residue  (see 
pages  64  and  66). 

Imitation  beans  have  frequently  been  sold  for  use  in  mixing 
with  coffee.  In  some  cases  these  are  molded  in  close  imita- 
tion of  the  true  beans.  The  material  used  for  the  purpose  is 
sometimes  clay,  but  more  frequently  one  or  more  of  the  fol- 
lowing: Wheat  flour,  chicory,  bran,  rye,  peas,  and  acorns. 
These  are  often  mixed  with  molasses.  Ferrous  sulfate  has  also 
been  found. 

Most  imitation  coffee  is  heavier  than  water,  but  the  readiest 
means  of  detection  is  by  means  of  the  microscope,  the  appli- 
cation of  the  iodin  test  for  starch,  and  determination  of  the  ash. 

Many  substances  have  been  used  as  substitutes  for  coffee  as 
well  as  for  its  adulteration;  among  these  are  chicory,  Mogdad 
and  Mussaenda  coffee,  roasted  cereals  and  leguminous  seeds, 
cocoa  husks,  and  figs. 

Coffee  contains  no  starch,  a  constituent  of  many  adulter- 
ants, such  as  cereals  and  acorns.  It  may  be  detected  by  Allen's 
method:  The  coffee  is  boiled  for  a  few  minutes  with  about 
ten  parts  of  water.  When  the  liquid  has  become  perfectly 
cold,  some  dilute  sulfuric  acid  is  added,  a  strong  solution  of 
potassium  permanganate  is  dropped  in  cautiously,  with  agita- 
tion, until  the  coloring-matter  is  nearly  destroyed,  when  the 
liquid  is  strained  or  decanted  from  the  insoluble  matter  and 
iodin  added.  A  distinct  reaction  occurs  in  the  presence  of 
even  i  per  cent,  of  starch.  In  identifying  the  starch  granules 
24 


266 


FOOD   ANALYSIS 


hp— 


-  qu 


with  the  microscope  it  is  advisable  to  make  a  preHminary  ex- 
traction of  the  sample  with  ether,  and  subsequently  with  alcohol. 
Chicory  is  the  root  of  the  Cichorium  intyhus  L.  Its  micro- 
scopic structure  distinguishes  it  from  coffee.  The  cells  of  the 
parenchyma  are  large,  smooth-walled,  and  regular.  The  milk 
ducts  are  branched  and  filled  with  a  coarsely  granular  material. 
The  body  of  the  root  contains  long,  pointed  cells  presenting  a 

characteristic  dotted  appear- 
ance. (See  Fig.  48.^')  It 
contains  no  starch.  Dande- 
lion and  other  sweet  roots 
\  V^l '^; i/^^^^t^^  '/fi^l  present  a  somewhat  similar 

\  V ^lli- i  =  :^ ^^^^0  \mlli  structure,  but  the  ducts  are 

\  ^^ipi^^^^S    if  /  /  scaliform,  the  cells  larger, 

and  milk  vessels  are  absent. 
Rimmington  recommends 
the  following  method  for  the 
detection  of  chicory:  The 
sample  is  boiled  for  a  short 
time  with  water  containing 
a  little  sodium  carbonate; 
the  solution  is  decanted  and 
the  residue  treated  with  a 
solution  of  bleaching  pow- 
der for  several  hours,  when 
decolorization  will  be  ef- 
fected. The  coffee  will  be 
found  as  a  dark  stratum  at  the  bottom  of  the  beaker  and  the 
chicory  as  a  light  stratum  above  it. 

Analytic  Methods. — The  following  preliminary  .tests  may 
be  of  value.  A  small  quantity  of  the  ground  material  is  sprin- 
kled on  cold  water.  Coffee  will  usually  float,  and  impart  very 
little  color  to  the  water.  Chicory  and  most  other  additions  sink, 
and  the  caramel  contained  in  them  dissolves  quickly,  forming 


Fig.  48. 
g,  Vascular  tissue;  hp,  parenchyma; 
fibers;  m,  medullary  rays. 


COFFEE  267 

a  dark  and  usually  turbid  solution.  Coffee  grains  are  hard, 
whereas  chicory  and  some  other  adulterants,  after  maceration 
for  some  hours  in  water,  are  quite  soft.  At  the  end  of  this  time 
if  the  mixture  be  transferred  to  a  piece  of  stretched  cloth  and 
rubbed  with  a  pestle,  the  chicory  will  pass  through. 

The  proportion  of  the  adulterant  which  has  been  detected 
by  the  microscope  or  the  preliminary  tests  just  mentioned  may 
often  be  determined  with  a  fair  degree  of  accuracy  by  chemi- 
cal examination,  especially  by  the  determinations  of  fat,  caf- 
fein,  water  extract,  and  ash. 

The  actual  amount  of  coffee  present  may  be  determined  by 
calculation  from  the  caffein  present  determined  by  the  process 
given  on  page  257,  using  double  the  quantity  of  material. 

In  the  presence  of  chicory  the  extracted  alkaloid  is  liable  to 
be  strongly  colored,  and  Allen  recommends  that  it  be  redis- 
solved  in  water,  a  few  drops  of  sodium  hydroxid  added,  and 
the  liquid  again  extracted  with  chloroform. 

Caffetannic  acid  may  be  determined  by  Krug's  method*®:  2 
graijis  of  the  material  finely  powdered  is  digested  for  36  hours 
with  10  c.c.  of  water  at  a  moderate  temperature,  then  25  c.c. 
of  90  per  cent,  alcohol  added  and  the  digestion  continued  for 
24  hours.  The  liquid  is  filtered  and  the  precipitate  washed 
with  90  per  cent,  alcohol.  The  filtrate  is  heated  to  boiling, 
and  a  boiling  concentrated  solution  of  lead  acetate  added. 
When  the  precipitate  (lead  caffetannate)  has  become  floccu- 
lent,  it  is  separated,  washed  on  the  filter  with  alcohol  (90%), 
until  the  washings  are  free  from  lead  (ammonium  sulfid  being 
used  as  a  test),  and  then  with  ether,  until  free  from  fat.  It  is 
dried  at  100°  and  weighed.  The  weight  multiplied  by  0.516 
gives  the  caffetannic  acid. 

The  proportion  of  caffein  in  roasted  coffees,  ranges  from  0.8 
to  1.3  per  cent.  In  the  better  grades  it  probably  does  not  go 
below  I.I  per  cent.,  1.2  might  be  taken  as  a  basis  of  calcula- 
tion. 


268  FOOD   ANALYSIS 

Fat. — The  fat  of  coffee  may  be  determined  by  extracting 
with  petroleum  spirit  or  carbon  tetrachlorid  the  material  dried 
at  1 00°.  According  to  Macfarlane,  the  petroleum  spirit  ex- 
tract from  previously  dried  coffee  usually  ranges  from  10  to  12 
per  cent.  Only  one  sample  out  of  nearly  fifty  showed  less  than 
10,  and  12.5  per  cent,  was  reached  only  in  a  few  cases. 

Water-extract. — Valuable  indications  are  often  furnished  by 
the  determination  of  the  amount  of  water-extract,  which  is 
fairly  uniform  and  little  affected  by  the  usual  variations  in  ex- 
tent of  roasting.  The  determination  is  simplified  by  the  ob- 
servation of  the  specific  gravity  of  the  solution  in  water  as 
recommended  by  Graham,  Stenhouse,  and  Campbell.  One 
part  of  the  sample  is  treated  with  ten  parts  of  water,  the  liquid 
heated  to  boiling,  cooled  to  15.5°,  and  the  specific  gravity  taken. 
The  following  figures  were  obtained  in  this  manner: 

Mocha  cofifee, 1008.0  Turnips, 102 1 .4 

Neilgherry  coffee, 1008.4  Dandelion, 102 1 .9 

Plantation  Ceylon  coffee, 1008.7  Red  beet, 1022. i 

Native  Ceylon  coffee, 1009.0  Marigold  wurzel, 1023 .5 

Java  coffee, 1008.7  Lupins, 1005 .7 

Jamaica  cofifee, 1008.8  Peas, 1007.3 

Costa  Rica  cofifee, 1009.0  Beans, 1008.4 

"  average, 1008.7  Brown  malt, 1010.9 

{1019.1  Black       "    1021.2 

to  Rye  meal, 102 1 .6 

1023.6  Maize, 1025.3 

"        average, 1021.0  Bread  raspings, 1026.3 

Parsnips, 1014.3  Acorns, 1007.3 

Carrots, 1017.1  Spent  tan, 1002. i 

According  to  McGill,  the  specific  gravity  of  the  infusions  of 
coffee  and  chicory  are  materially  affected  by  the  fineness  of 
powder  and  the  time  occupied  in  heating  the  solution  to  boiling, 
and  the  duration  of  the  boiling.  He  recommends  the  following 
process:  10  grams  of  the  dried,  finely  powdered  sample  are 
heated  with  100  c.c.  of  distilled  water  in  a  flask  provided  with 
a  reflux  condenser.     The  heat  is  adjusted  so  that  ebulHtion 


COFFEE  269 

commences  in  10  to  15  minutes,  and  the  boiling  continued  for 
exactly  one  hour;  the  liquid  is  allowed  to  stand  for  15  minutes, 
and  then  passed  through  a  dry  filter.  The  average  specific 
gravity  of  the  decoction  from  pure  coffee  was  found  to  be 
1009.86  at  17°,  and  that  of  chicory,  1028.21.  The  amount  of 
coffee  present  in  a  mixture  of  coffee  and  chicory  may  be 
approximately  calculated  by  deducting  the  observed  gravity 
from  1028.21  and  multiplying  the  remainder  by  5.45. 

Macfarlane  has  determined  the  water  extract  by  boiling 
with  water  the  dried  residue  from  the  determination  of  fat 
(page  268)  and  redrying  and  weighing  the  residue.  The 
water-extract  is  determined  by  difference.  The  following 
results  were  obtained : 

Cofifee  (Santos,  Mocha,  and  Java), 20.4-22.4  per  cent. 

Chicory, 77.7  "       " 

Hehner  has  found  highly  roasted  chicory  to  give  a  water-ex- 
tract as  low  as  54.1  per  cent,  and  a  specific  gravity  of  the  10 
per  cent,  solution  of  1019. 

Cassal  has  found  genuine  coffee  to  give  a  water-extract  as 
high  as  29  per  cent.  More  recently  several  observers  have 
called  attention  to  the  fact  that  the  proportion  of  water-soluble 
matter  in  commercial  chicory  may  be  markedly  greater  than 
that  found  in  the  above  samples,  examined  years  ago.  This 
appears  to  be  due,  as  pointed  out  by  Dyer,  to  the  less  roasting 
to  which  it  is  subjected.  The  following  results,  due  to  Dyer, 
were  obtained  by  boiling  the  sample  with  water,  washing,  dry- 
ing, and  weighing  the  insoluble  residue,  and  determining  the 
soluble  matters  by  difference.  The  moisture  varied  in  extreme 
cases  from  i  to  4  per  cent.,  but  the  results  were  calculated 
as  percentage  of  the  dried  material: 


270  FOOD   ANALYSIS 

Insoluble  Ash 

IN  Ether-  Nitro-    Total  Soluble  in 

Water.  extract,  gen.        Ash.       Water.       Sand. 

Chicory  "nibs"   described  as 

"medium  roast," 22.40  2.57  1.53        4.63        2.50        0.70 

Chicory  "nibs"   described  as 

"dark  roast," 5o-30  2.43  1.67        4.70        2.99        0.30 

f    21.50  1.90  1.23        5.33        1.60       0.77 

Ground  chicory,  9  samples, .  j       to  to  to,           to           to           to 

i   37.80  3.87  1.52        8.23        3.30       3.97 


In  eight  out  of  the  eleven  samples  the  matter  insoluble  in 
water  ranged  from  21.50  to  23.50  per  cent.  One  sample  con- 
tained 35.50,  one  37.80,  and  one  50.30  per  cent. 

Graham,  Stenhouse,  and  Campbell  have  suggested  the  tinc- 
torial power  of  the  infusion  as  a  means  of  determining  adul- 
terants in  coffee.  As  a  rule,  the  coloring  power  of  chicory  is 
about  three  times  as  great  as  that  of  coffee.  The  method 
may  be  useful  in  the  detection  of  added  caramel  or  of  added 
sugar  which  has  been  caramelized  in  roasting.  The  infusion 
should  be  compared  with  that  from  pure  coffee. 

The  ash  of  coffee  is  usually  3.5  to  4.5  per  cent.,  and  rarely, 
if  ever,  5  per  cent.  Of  this,  about  80  per  cent,  is  soluble  in 
water.  It  contains  mere  traces  of  silica,  and  is  almost  in- 
variably white.  A  red  ash  usually  indicates  adulteration.  A 
notable  amount  of  potassium  is  present,  but  sodium  may  be 
present  in  small  amount.  Analyses  by  Ludwig  indicate  that 
the  composition  of  coffee  ash  is  subject  to  marked  variation 
according  to  soil.  Chicory  contains  about  6  per  cent,  of  ash, 
of  which  only  from  30  to  40  per  cent,  is  soluble  in  water.  It 
may  contain  several  per  cent,  of  silica  and  usually  carries  con- 
siderable admixed  sand.  Sodium  is  always  present,  often  to  a 
considerable  extent. 

The  ash  of  cereals  and  leguminous  seeds  is  usually  less  than 
that  of  coffee  (see  page  95). 

The  following  table,  due  to  Konig,  gives  some  results  ob- 
tained from  the  examination  of  various  coffee  adulterants : 


COFFEE  271 

Water- 
extract 
Calcu- 
lated 
NiTRO-      Ether-  on  the 

GENOUS  EX-  N-FREE  DrY  MA- 

Water.  Matter,     tract.    Sugar.    Matter.  Fiber.    Ash.    terial. 

Chicory,  roasted,.. 1 3. 1 6  6.53        2.74      17.89      41.42      12.07    6.19     70.50 

Figs,  roasted, 1250  4.57       2.96      32.50      31.92      12.34    5.21     82.50 

St.     John's    bread  ' — . — ' 

(carob  bean),  ...  5.35  8.93        3.65            69.83             10.15    2.09     63.71 

Cereals  (rye,  etc.),..  1 2. 50  12.15        3-57        4-i2      55-66       8.45    3.55     48.53 

Malt, 7.08  13.05        2.25      15.67      51.74        7.38    2.83     65.00 

Mogdad  cofiFee(Ca5- 

sia  occidentalis),. II. og  15.13        2.55            46.69              21.21    4.33     30.00 
"Congo"       cofifee, 

raw, ....13.72  39.82        1.26           37.09               4.41    3.70 

"Congo"       coffee, 

roasted, 4.22  27.06        1.19        3,25      39.74      19.28    4.63     22.50 

Acorns,  shelled  and 

roasted, 12.50  6.78       4.35            69.27                5.02    2.07     28.88 

Date  stones, 9.27  5.46       8.50           52.86             23.97    1.44     12.87 

Fruit  of  wax  palm, 

raw, 9.37  6.54      10.57        1.67      25.48     44.31    2.06     13.41 

Fruit  of  wax  palm, 

roasted, 3.76  6.99      14.06        1.25      33.25      38.45    2.24     14.03 

A  number  of  methods  have  been  proposed  for  the  deter- 
mination of  the  caramel  in  coffee  roasted  with  sugar.  A 
method  due  to  Hilger  is  as  follows:  10  grams  of  the  whole 
coffee  are  shaken  for  half  an  hour  each  time  with  three  suc- 
cessive portions  of  100  c.c.  of  a  mixture  of  equal  parts  of  water 
and  85  per  cent,  alcohol.  The  united  solutions  are  made  up 
to  500  c.c,  filtered,  the  residue  dried  at  100°,  weighed,  and  the 
ash  determined  and  deducted.  It  is  necessary  to  decant  the 
liquid  from  the  berries  before  filtering,  since  the  extra  time 
considerably  increases  the  relative  amount  of  ash  in  the  extract, 
due  to  the  more  complete  extraction  of  the  constituents  of  the 
berry  itself.  Fresenius  &  Griinhut  consider  that  the  best 
results  are  had  by  deducting  from  the  result  a  mean  constant 
for  the  materials  extracted  from  the  cofifee  itself. 

The  following  results  were  obtained.     The  roasting  of  the 


272 


FOOD  ANALYSIS 


coffee  without  sugar  was  performed  in  the  normal  manner; 
i.  e.,  the  loss  on  roasting  was  about  18  per  cent. : 

Soluble  Residue 
(Less  Ash). 

Yellow  Java, 0.71 

Green      "     0.62 

Blue         "     1.39 

Maracaibo,   0.60 

Average, 0.83 

Percentage  of  Ash- 
free  Soluble  Matter 
Less  0.83. 

Yellow  Java  roasted  with  7I  per  cent,  of  sugar, 2.21 

2.83 

2.06 

3-46 

2.55 

4.00 

2.78 

3-39 


9 

Green      " 

"    7h 

11         (( 

"    9 

Blue 

"    7i 

t(                <c 

"    9 

Maracaibo 

"     7i 

" 

"    9 

Coffee  Extracts. — Many  attempts  have  been  made  to  pre- 
pare a  concentrated  infusion  of  coffee,  but  the  results  have 
not  been  satisfactory.  In  most  cases  preservatives  are  neces- 
sary. Some  preparations  contain  excessive  proportions  of 
sugar,  and  occasionally  caffein  is  added  to  enrich  the  mixture. 
Moor  &  Priest  give  the  following  analyses  of  English  prepara- 
tions : 


Coffee  extract 


Total  Solids.    Ash. 

39-9  4-25 

27.9  0.95 

with  chicory, 30.0  0.36 

34.8  1.28 

46.4  0.43 

with  chicory, 37.6  0.36 

50-6  0.55 

with  chicory, 48.6  1.87 

"     sugar, 51.5  2.50 

"     chicory, 48.5  1.14 


Nitrogen.  Caffein. 


0.96 
0.15 


0.23 
0.06 


0.41 

0-37 
0.38 
0.30 


1.98 
0.47 
0.32 
0.54 
0-57 
0.02 
0.56 
.0.26 
0.61 
0.28 


In  the  first  sample  caffein  has  probably  been  added. 
Essence   of  Coffee. — Coarsely   broken   cereals   roasted 


with 


CACAO   AND   CHOCOLATE  273 

molasses  have  sold  under  this  title.  The  nature  of  the  material 
may  usually  be  determined  by  simple  inspection.  Of  late  years, 
the  term  "essence  for  coffee"  has  been  substituted. 

The  starch  in  the  original  material  will  be  somewhat  changed 
both  in  chemical  and  physical  characteristics,  but  the  reaction 
with  iodin  and  the  microscopic  characters  will  generally  assist 
in  the  recognition  of  the  cereals  present. 

CACAO  AND  CHOCOLATE 

Cacao  is  prepared  from  the  seeds  of  Theobroma  cacao  L.  The 
fruit  contains  from  25  to  40  slightly  ovate  flattened  seeds,  1.5 
to  2.5  cm.  long  and  0.6  to  1.5  cm.  broad,  which  are  colorless 
when  first  removed  from  the  pulp,  but  become  yellow,  red,  or 
brown  on  exposure.  They  are  dried  in  the  sun,  either  at  once 
or  after  being  subjected  to  fermentation  (brought  about  in 
some  cases  by  burial),  which  removes  the  pulp  and  much  of  the 
acridity  and  bitterness. 

Cacao  seeds  contain  theobromin,  caffein,  fat,  tannin,  starch, 
gum,  proteids,  and  tartrates.  The  taste  and  odor  are  due  to 
volatile  materials  developed  in  roasting. 

Theohromiriy  dimethylxanthin,  crystallizes  in  colorless, 
minute,  rhombic  needles.  One  part  is  soluble  in  the  following 
parts  of  solvents:  cold  water,  1600;  boiling  water,  148;  cold 
alcohol,  4280;  boiling  alcohol,  400;  cold  ether,  1700;  boiHng 
ether,  600;  boiling  chloroform,  105.  It  is  insoluble  in  petro- 
leum spirit.  It  dissolves  in  acid  and  alkahne  solutions,  especially 
in  ammonium  hydroxid,  and  is  completely  extracted  from  alka- 
line solution  by  chloroform.  When  the  solution  in  ammo- 
nium hydroxid  is  mixed  with  silver  nitrate  and  heated  for  a 
considerable  time,  a  silver  compound  is  precipitated. 

Kunze  has  examined  the  methods  for  the  separation  of  the 
alkaloids,  and  found  all  defective.  In  estimating  the  alkaloids 
of  cacao  previous  rernoval  of  the  fat  is  not  advisable,  as  some 
alkaloid  is  extracted.    Kunze  recommends  the  following  process : 


274  FOOD   ANALYSIS 

The  material  is  boiled  for  30  minutes  with  normal  sulfuric 
acid,  filtered,  and  a  large  amount  of  a  solution  of  sodium 
phosphomolybdate  in  nitric  acid  added.  The  precipitate, 
which  usually  settles  rapidly,  is  removed  by  filtration  after  24 
hours,  washed  with  dilute  sulfuric  acid,  and  at  once  decom- 
posed by  treatment  with  barium  hydroxid  solution,  the  excess 
of  barium  hydroxid  being  removed  by  carbon  dioxid.  The 
liquid  and  precipitate  are  evaporated  to  dryness  and  the  residue 
extracted  with  boiling  chloroform.  The  chloroform  solution, 
on  evaporation,  leaves  the  alkaloids  almost  perfectly  pure,  and 
containing  only  a  trace  of  ash. 

Sodium  phosphomolybdate  solution  is  prepared  as  follows: 
A  warm  solution  of  disodium  hydrogen  phosphate  is  acidu- 
lated with  nitric  acid  and  an  excess  of  ammonium  molybdate 
solution  added.  The  precipitate  is  washed  with  water  con- 
taining nitric  acid  and  dissolved  in  a  hot  solution  of  sodium 
carbonate.  The  liquid  is  evaporated  to  dryness,  the  residue 
ignited  at  a  low  red  heat  until  all  ammonium  is  volatilized, 
moistened  with  nitric  acid,  and  again  ignited,  i  gram  of  the 
product  is  dissolved  in  10  c.c.  of  water  and  i  c.c.  of  nitric  acid 
(sp.  gr.  1.42)  added. 

Separation  of  the  alkaloids  may  be  effected  by  converting 
the  theobromin  into  a  silver  compound.  The  mixture  of  alka- 
loids is  dissolved  in  ammonium  hydroxid,  a  considerable  ex- 
cess of  nitrate  is  added,  the  solution  boiled  down  to  small  bulk, 
and  until  all  free  ammonia  is  expelled.  The  crystalline  pre- 
cipitate is  collected,  washed  with  boiling  water,  ignited,  and 
the  metallic  silver  weighed.  The  process  may  be  made  volu- 
metric by  titrating  the  excess  of  silver  in  the  filtrate  by  Vol- 
hard's  method.  In  the  latter  case  the  alkaloids  may  be  .readily 
isolated  from  the  precipitate  and  the  filtrate  (after  titration), 
and  tested  as  to  their  purity,  identity,  etc.  The  separation 
of  caffein  from  theobromin  by  means  of  benzene  is  imperfect. 

The  proportions  of  theobromin  given  by  different  observers 


CACAO   AND   CHOCOLATE  275 

differ  greatly,  owing  in  part  to  the  methods  employed.  The 
average  of  the  reported  data  is  about  1.5  per  cent.  Kunze 
found  by  his  method  1.2  per  cent,  total  alkaloids.  Weigmann 
obtained  the  following  results: 

Beans.  Husks. 

Theobromin,  per  cent., 1.26  0.50 

Cafifein,  percent., 0.17  0.15 

According  to  Stutzer,  the  nitrogenous  constituents  of  cacao 
are  of  three  types: 

1.  Non-proteids,  not  precipitated  by  copper  hydroxid  (the- 
obromin, caffein,  and  amido- compounds). 

2.  Digestible  albumin,  insoluble  in  pure  water  in  presence 
of  copper  hydroxid,  but  soluble  when  treated  successively  with 
acid  gastric  juice  and  alkaHne  pancreatic  extract. 

3.  Insoluble  and  indigestible  nitrogenous  matter. 

He  gives  analyses  of  three  samples,  showing  the  relative  pro- 
portion of  these  forms : 

Nitrogen   as   soluble   compounds,    in- 
cluding that  of  alkaloids, 3 1  -43  2 6.95  29 . 79 

Nitrogen  as  digestible  albumin, 33-34  40.61  22.62 

Nitrogen  as  indigestible  matter, 35-33  32.44  47-^3 


Fat. — The  so-called  cacao-butter  is  a  yellowish- white  solid, 
of  pleasant  odor,  melting  between  28°  and  30°.  Further  data 
in  regard  to  it  are  given  in  connection  with  the  fats. 

Cacao-red. — This  appears  to  be  an  oxidation  product  of  the 
tannin.  It  does  not  exist  as  such  in  the  cacao.  It  may  be 
prepared  from  the  aqueous  or  alcoholic  decoction  by  pre- 
cipitating with  lead  acetate  and  decomposing  the  washed  pre- 
cipitate with  hydrogen  sulfid.  The  colorless  Hquid  so  obtained 
becomes  red  on  evaporation.  Cacao-red  is  slightly  soluble  in 
cold  water,  much  more  so  in  hot. 

Gum. — About  2  per  cent,  of  gum  resembling  gum  arable  is 


276 


FOOD  ANALYSIS 


present.  It  is  precipitated  by  alcohol  from  the  watery  extract 
of  the  fat-free  cacao.     It  is  dextrorotatory. 

Tartaric  Acid. — This  has  been  found  to  be  present  to  the 
extent  of  several  per  cent.  Weigmann  estimates  it  by  neu- 
tralizing the  aqueous  extract  with  ammonium  hydroxid,  add- 
ing calcium  chlorid,  redissolving  the  precipitate  in  hydro- 
chloric acid,  and  reprecipitating  with  sodium  hydroxid.  From 
4.34  to  5.85  per  cent,  of  tartaric  acid  were  found  in  this  way. 

Starch. — The  granules  of  cacao-starch  are  very  small;  their 
microscopic  characters  are  given  on  page  90.  Samples  of  cacao 
examined  by  Ewell  contained  from  5.78  to  15.13  per  cent,  of 
starch. 

Mineral  Matter. — The  ash  of  cacao  consists  largely  of  phos- 
phates with  but  little  chlorids  and  carbonates.  The  amount 
of  magnesium  exceeds  notably  that  of  the  calcium.  The  pro- 
portion of  sodium  is  small,  and  traces  of  copper  are  usually 
present.     The  proportion  of  husk  ranges  from  8  to  15  per  cent. 

ANALYSES  BY  J.  BELL 


Per  100   OF 
Cacao. 

Per  100  OF  Ash. 

Water. 

Ash  (on 
Dry 
Sub- 
stance). 

Soluble 

in 
Water. 

Insol. 

in 
Acid. 

Phos- 
phoric 
Oxid. 

Carbon 
Dioxid. 

Potas- 
sium 
Oxid. 

Fer- 
rous 
Oxid. 

Guayaquil  nibs  (i. 
e.,  husked),   .    . 

5.06 

3.63 

56.3 

None 

49.4 

0.69 

23-4 

0.21 

Surinam  nibs,    .    . 

4-55 

2.90 

43.5 

None 

378 

Z-Z^ 

28.0 

0.38 

Grenada  nibs,    .    . 

571 

2.82 

48.6 

None 

39-2 

2.92 

27.6 

0.15 

Finest  Trinidad 

nibs, 

4-47 

2.75 

46.6 

None 

36.2 

4.19 

29-3 

0.  II 

Finest  Trinidad 

. 

husks,     .... 

10.19 

8.63 

54-9 

591 

17.2 

10.8 

37-9 

0.63 

The  important  commercial  cacao  preparations  are : 

Plain  chocolate,  which  consists  of  the  roasted  and  husked 


CACAO   AND  CHOCOLATE 


277 


seeds,  ground  to  a  paste  while  quite  hot  and  pressed  into  cakes. 
This  is  known  in  Europe  as  ''cacao  masse." 


ANALYSES  BY  H.  WEIGMANN 


Raw,  unhusked, 

Roasted,    " 

*•         husked 
(nibs),     .    .    . 

Cacao  masse, 
(plain  choco- 
late),       .    .    . 

Husks  (contained 
4.06  per  cent, 
sand), .... 


Mois- 
ture. 


7-93 
6.79 

5.58 

4.16 

11.73 


Nitro- 
genous 
Matter. 


14.19 
14.13 

14.13 

13.97 
13.95 


Thko- 

BROMIN. 


1.49 

1.58 

1.55 
1.56 

073 


Fat. 


45-57 
46.19 

50.09 

53-03 
4.66 


Starch. 


5.85 
6.06 

8.77 


Other 

NlTRO- 
GEN-FREE 

Matter. 


17.07 
18.04 

13-91 


9.02         12.79 


43.29 


Fiber. 


4.78 
4.63 


4.61 
4.16 


3-93  I  3-59 


3-40 


16.02 


3.63 


10.71 


Sweet  chocolate  is  the  mixture  of  the  above  with  50  per  cent, 
or  more  of  sugar,  and  flavoring  materials,  such  as  spices  and 
viinilla. 

Cacao  essence,  or  cacao  powder,  is  prepared  by  removing 
from  the  husked  and  roasted  bean,  by  means  of  heat  and  pres- 
sure, a  portion  (usually  about  one-half)  of  the  fat. 

The  so-called  soluble  "cocoas"  are  prepared  by  treating  the 
above  with  ammonium  hydroxid,  sodium  or  potassium  carbon- 
ate, or  steam  to  destroy  the  cellular  structure,  to  convert  the  pro- 
teids  into  more  soluble  modifications,  but  more  especially  to 
emulsify  the  fat  so  that  it  may  not  come  to  the  surface  when 
the  decoction  is  made.  The  treatment  with  alkaline  carbonate 
is  practised  by  the  Dutch  manufacturers.  The  term  soluble  in 
connection  with  such  preparations  is  not  accurate,  as  is  evident 
from  the  following  analyses  made  by  Stutzer: 

I.  Made  from  a  mixture  of  Ariba,  Machala,  and  Bahia 
cacao  without  the  use  of  chemicals. 

II.  Dutch  cacao. 


278  FOOD   ANALYSIS 

III  and  IV.  German  cacao  prepared,  in  Stutzer's  opinion, 
by  the  use  of  ammonium  hydroxid. 

I.  II.  m.  IV. 

Water, 4.30  3.83  6.56  5.41 

Fat, 27.83  30.51  27.34  33-85 

Fiber, 3.361  „  ^    ^ 

Nitrogen-free  extract 38-62/  ^''^^  ^^'^^  3*°* 

Total  nitrogenous  substances  (i), 20.84  19.88  20.93  19-25 

Ash(2),   5.05  8.30  5.18  5.43 

(i).  Total  nitrogen, 3.68  3.30  3.95  3.57 

Theobromin, 1.92  1.73  1.98  1,80 

Ammonia, 0.06  0.03  0.46  0.33 

Amido-compounds, 1.43  1,25  0,31  1.31 

Digestible  albumin, 10.25  7-68  10.50  7.81 

Indigestible  nitrogenous  matters, .  7.18  9.19  7.68  8.00 

Containing  nitrogen, 1.15  1.47  1.23  1.28 

Proportion  of  total  nitrogen  indi- 
gestible,   31.2    ,  44.5  32.2  35.8 

(2)    Phosphoric  oxid, 1.85  2.52  2.14  2.05 

"                  "     soluble  in  water,   1.43  0.50  0.74  0.77 

Ash  soluble  in  water, 3-76  4.76  2.86  2.76 

Stutzer  considers  that  the  addition  of  alkalies  is  unneces- 
sary, since  the  good  results  may  be  had  from  the  untreated 
bean,  if  the  preparation  and  roasting  be  properly  conducted. 
U.  S.  Standard. 
Plain  or  hitter  chocolate. 
Ash  insoluble  in  water,  not  over  .  3.0   per  cent. 
Crude  fiber  ''      "      .  3.5      "      " 

Starch  ''      "      .  9.0      ''      " 

Cacao-fat  not  less  than  .45.0 

Sweet  chocolate  and  chocolate  coatings  are  plain  chocolate 
mixed  with  sugar  (sucrose),  with  or  without  the  addition  of 
cacao  butter,  spices  or  other  flavoring  materials,  and  contain 
in  the  sugar-free  and  fat-free  residue  no  higher  percentage  of 
either  ash,  fiber  or  starch  than  is  found  in  the  sugar- free  and  fat- 
free  residue  of  plain  chocolate. 


CACAO  AND  CHOCOLATE  279 

Cacao  or  powdered  cacao  is  cacao  nibs,  with  or  without  the 
germ,  deprived  of  a  portion  of  its  fat  and  finely  pulverized,  and 
contains  percentages  of  ash,  crude  fiber  and  starch  corresponding 
to  those  in  chocolate  after  correction  for  fat  removed. 

Sweet  or  sweetened  cacao  is  cacao  mixed  with  sugar  (sucrose) 
and  contains  not  more  than  60  per  cent,  of  sugar  (sucrose),  and 
in  the  sugar- free  and  fat- free  residue  no  higher  percentage  of 
either  ash,  crude  fiber,  or  starch  than  is  found  in  the  sugar- 
free  and  fat-free  residue  of  plain  chocolate. 

Adulterations. — The  finest  grades  of  cacao  are  made  from 
the  cotyledons  only.  The  husks  are  occasionally  added  to  the 
cheaper  grades  of  chocolate.  On  account  of  the  large  pro- 
portion of  a  fat  in  cacao  (usually  abouf  50  per  cent.),  it  is  im- 
possible to  prepare  from  it  a  permanent  powder  unless  a  part  of 
the  fat  be  removed  or  a  diluent  such  as  starch  or  sugar  be  added. 
In  many  cases  more  than  half  of  the  fat  is  allowed  to  remain. 
The  common  adulterants  of  cacao  powder  are  sugar,  starches, 
and  flours.  The  color  of  the  diluted  material  may  be  improved 
by  the  addition  of  brown  iron  oxid  or  artificial  colors.  Cop- 
per sulfate,  potassium  chromate,  and  nickel  sulfate  are  said  to 
have  been  added.  Chocolate  is  often  adulterated  with  ground 
peanuts,  almond  cake,  and  similar  material.  In  some  cases 
a  portion  of  the  fat  is  removed  and  foreign  fat  substituted. 
Finely  divided  tin  is  stated  to  have  been  added  in  order  to  im- 
part a  metallic  luster. 

Analytic  Methods. — A  careful  examination  under  the 
microscope  should  be  made  in  order  to  determine  the  pres- 
ence of  husks,  foreign  starches,  peanut,  almond,  or  other  ad- 
ditions. A  determination  of  the  ash,  and  of  its  solubility  and 
alkalinity,  should  be  made.  The  ash  of  pure  cacao  is  white, 
and  usually  under  4  per  cent.,  if  prepared  from  the  cotyledons 
only.  A  higher  proportion  may  point  to  the  presence  of  husks, 
added  mineral  matter,  or  the  use  of  alkali  in  the  manufacture. 


28o  FOOD   ANALYSIS 

(See  tables,  pp.  27  and  41.)  The  moisture  and  fat  should  be 
determined  as  on  pages  278  and  282.  The  extraction  of  the  fat 
should  be  performed  by  means  of  petroleum  spirit.  The 
material  extracted  may  be  examined  for  foreign  fats  as  described 
on  page  179.  In  the  case  of  cacao  prepared  by  the  use  of  alkali 
an  appreciable  amount  of  soap  will  be  present,  which  will  re- 
main undissolved  by  the  petroleum  spirit.  It  may  be  separated 
by  treating  the  residue  with  alcohol  acidified  with  hydro- 
chloric acid,  evaporating  to  dryness,  and  shaking  with  water  and 
ether.  The  fatty  acids  are  recovered  from  the  ether  by  evapora- 
tion. 

The  determination  of  the  theobromin  and  caffein  may  be 
made  as  described  on  page  273.  The  determination  of  total 
nitrogen  is  easier.  The  following  analyses  by  Bitteryst  show 
the  use  of  such  determination: 

Percentage  of  Proteids. 

Pure  chocolate, 9.10 

"     cacao, 17.57 

Peanuts, 28.18 

Peanut-cake, 46.90 

Pure  chocolate  +  10  per  cent,  of  peanuts, 12.53 

"  "        +  10        "         peanut-cake, i5-7o 

"     cacao        +  10        "  "  21.18 

Sugar. — Exact  determinations  of  sugar  are  difficult,  but 
approximations  quite  sufficient  for  practical  purposes  may  be 
made  by  the  polarimeter.  The  gum  introduces  an  error  rang- 
ing from  0.3  to  2.0  per  cent.  To  avoid  interference  from  starch, 
the  solution  must  be  made  with  cold  water.  Ewell  has  found 
that  it  is  necessary  to  use  about  40  c.c.  of  water  for  each 
gram  of  sample.  The  following  process,  described  by  Ewell, 
is  adapted  to  a  polarimeter  requiring  a  concentration  of  26.048 
grams:  13.024  grams  of  material  are  triturated  with  alcohol  to 
a  smooth  paste,  which  is  transferred  to  a  500  c.c.  flask,  diluted 
with  400  to  450  c.c.  of  water,  and  shaken  occasionally  during  four 


CACAO   AND   CHOCOLATE  28 1 

hours;  after  which  10  c.c.  of  a  saturated  solution  of  lead  acetate 
are  added,  the  volume  brought  to  500  c.c,  and  allowed  to  stand 
for  one  hour,  with  occasional  shaking.  The  solution  is  filtered 
and  the  polarimetric  reading  taken.  If  a  200  mm.  tube  is  used 
the  reading,  multiplied  by  10,  will  give  results  close  enough, 
since  there  is,  as  noted  above,  an  indefinite  error  from  the  gum 
in  solution.  Ewell  prefers  to  allow  for  the  volume  of  the  pre- 
cipitate, and  has  given  a  formula  which,  reduced  to  a  simpler 
form  than  as  he  presents  it,  is,  for  the  200  mm.  tube : 

Percentage  of  sugar  =  9.76  R  -f  0.0130  R';  R  being  the  observed  reading. 

Starch. — This  is  determined  by  the  method  given  on  page  93, 
the  sugar  being  first  removed  by  cold  water. 

Crude  Fiber. — This  is  determined  as  on  page  38.  Little 
reliance  can  be  placed  upon  many  published  figures  for  this 
datum,  on  account  of  the  differences  in  methods  employed. 

Alkalies. — For  detecting  the  use  of  alkalies  in  the  manu- 
facture of  cacao  the  following  data  may  be  determined :  Total 
ash,  water-soluble  ash,  total  phosphate  and  that  in  the  cold 
water  solution,  expressed  as  phosphoric  oxid.  The  relative 
proportions  of  these  constituents  in  the  ash  of  normal  cacao 
and  of  cacao  treated  with  fixed  alkalies  and  ammonia  are  given 
in  the  table  on  page  278.  Additional  evidence  of  the  use  of 
ammonia  is  obtained  by  distillation  of  the  sample  with  mag- 
nesia and  determination  of  the  ammonia  in  the  distillate. 
If  this  process  yields  more  than  o.i  per  cent,  of  nitrogen  in 
the  form  of  ammonia,  Stutzer  considers  the  result  certain  evi- 
dence of  the  use  of  ammonia  or  ammonium  salts  in  the  manu- 
facture. 

The  following  table  gives  some  of  the  results  obtained  by 
Ewell  from  an  examination  of  cacao  preparations  as  found  in 
the  American  market: 


25 


282 


FOOD  ANALYSIS 


Foreign 
Starches. 

Water 

Fat. 

Cane- 
sugar 

BY 

Polar. 

Crude 
Fiber. 

Total 
Ash. 

^ACID 
10 

Req.  to 

Neu- 
tral- 
ize 
Ash  of 
I  Gram. 

Plain  Chocolates  ; 

c.c. 

Chocolate,      .    . 

None. 

318 

50.84 

2.91 

3-44 

255 

Much  wheat 
starch. 

309 

49.81 

2.63 

3.08 

2.12 

Much  wheat 
flour. 

3.82 

49.40 

2.74 

3.18 

2.30 

Sweet  Chocolates  : 

"Instantaneous 
Chocolate,"    . 

None. 

1.88 

24.04 

53 

1.32 

1.69 

1-45 

"Powdered,"    . 

None. 

1-55 

1773 

65 

0.94 

I. 21 

0.75 

"Princess,"   .    . 

None. 

1.46 

25-74 

55 

1. 14 

1-54 

0.92 

"Vanilla,"    .    . 

None. 

0.65 

22.49 

57 

1.23 

1.52 

I.OO 

Cocoas  and  B  row  as: 

Breakfast  Cocoa, 

None. 

25.83 

.    . 

4.23 

5-05 

3-65 

Cocoa  Extract,  . 

None. 

.    . 

30.95 

.    . 

3-89 

4.24 

2.9 

Dutch  Cocoa,     . 

None. 

31.48 

3.76 

6.06 

4.8 

Breakfast  Cocoa, 

Wheat    flour 
and  arrow- 
root. 

35.85 

308 

3-84 

2.6 

Prepared  Cocoa, 

Much  arrow- 
root. 

25-94 

26 

I  51 

3-15 

1-3 

CONDIMENTS  AND  SPICES 


VINEGAR 

Vinegar  is  the  acid  liquid  resulting  from  the  acetous  fer- 
mentation of  various  decoctions  or  fruit  juices.  Acetic  acid 
is  the  prominent  constituent,  but  small  amounts  of  alcohol, 
aldehyde,  and  ethyl  acetate  are  usually  present,  together  with 


VINEGAR  283 

extractive  matters  depending  upon  the  nature  of  the  material 
used.  Very  dilute  solutions  of  acetic  acid  do  not  keep  well, 
and  a  little  alcohol  is  regarded  by  some  persons  as  desirable, 
improving  the  flavor  and  keeping  qualities.  Some  mineral 
acid  was  formerly  thought  to  be  necessary  as  a  preservative. 
Such  addition  is  not  needed,  but  is  sometimes  practised  as  an 
adulteration.  Sulfuric  acid  is  usually  employed,  rarely  hy- 
drochloric. 

Vinegar  is  often  made  by  spontaneous  fermentation,  but 
malt  and  spirit  vinegars  are  mostly  made  by  passing  dilute 
alcohol  over  shavings  impregnated  with  the  acetic  ferment, 
a  regulated  supply  of  air  being  maintained  at  the  same  time. 
The  conversion  of  the  alcohol  into  acetic  acid  is  rapid. 

Wine,  cider,  malt,  and  spirit  vinegar  are  the  chief  forms. 

Wine  Vinegar. — That  from  white  wine  is  most  esteemed. 
It  usually  contains  between  5  and  10  per  cent,  of  acetic  acid, 
1.5  and  3  per  cent,  of  solids,  and  0.2  and  0.6  per  cent,  of  ash. 
The  extract  contains  from  0.25  to  0.5  per  cent,  of  acetic  potas- 
sium tartrate.  The  following  analyses  of  true  vinegar  result- 
ing from  four  months'  fermentation  are  by  Farnsteiner: 

I.  2.  3. 

Alcohol, 3.75  0.00  1 .23 

Acid, 3.56  7.60  6.00 

Solids, 2.03  3,64  2.56 

Ash, 0.28  0.30  0.34 

Alkalinity  of  ash  in  c.c.  of  normal  alkali,..  .1.78  2.90  2.85 

Small  amounts  of  sugar,  glycerol,  and  tartaric  acid  are  pres- 
ent in  each  sample. 

U.  S.  Standard. 

Acetic  acid     not  less  than  -.4  grams  in   100  c.c. 

Grape  solids     "  ''       ''  ..1.4          "       " 

Grape  ash         "  "       "  ..0.13        "       '' 

In  the  United  States,  spirit  vinegar  made  from  the  dilute 
alcohol  called  "low  wine"  is  often  sold  as  white  wine  vinegar. 


284  FOOD   ANALYSIS 

Cider  vinegar  is  a  brownish  liquid  containing  about  4  per 
cent,  of  acetic  acid  and  2  per  cent,  of  solid  matter  which  has 
the  odor  and  taste  of  apples.  It  is  frequently  imitated  by  spirit 
vinegar  or  diluted  acetic  acid  colored  with  caramel.  G.  S. 
Cox  and  A.  W.  Smith  have  published  analyses  of  commer- 
cial cider  vinegars.  The  former  found  in  20  samples  a  per- 
centage range  of  acidity  from  2.3  to  8.4,  solids  1.34  to  4,  ash 
0.25  to  0.52.  Smith  examined  51  samples,  22  of  which  were 
genuine,  27  diluted  with  water  or  spirit  vinegar,  one  made  from 
dried  apples  and  glucose,  and  one  made  from  cider  and  grape- 
juice.  The  following  table  shows  the  differences  in  important 
data: 

Grams  per  Milligrams  per  ioo 

100  Grams  of  Vinegar:  Grams  of  Vinegar: 

^  Phosphoric  Phosphoric 

CO.           acid  Oxid  in           Oxid  in 

10  Soluble           Insoluble 

Acid.       Solids.        Ash.                for  ash.  Ash.                 Ash. 

Maximum, 7.61        4.45        0.51'  55.2  22.7  19.4 

Minimum, 3.24        2.00        0.31  28.4  13.6  4.2 

Average, 4.46        2.83        0.39  38.8  19. i  10. i 

Cider  vinegar  di- 
luted with 
water  or  spirit 
vinegar: 

Maximum, 4.83        3.41        0.53  29.6  15.2  20.2 

Minimum, 3.01        1.19        0.14  1.4  0.00  3.0 

Average, 4.00        2.03        0.24  18.4  5.2  5.7 

Sample  from  dried 
apples  and  glu- 
cose,  4.29        3.89        0.25  21.0 

Sample  from  cider 

and  grape-juice,  4.54        2.77        0.30  34.0 

Smith  finds  that  the  ash  of  cider  vinegar  begins  to  melt  and 
volatilize  at  a  comparatively  low  temperature  and  gives  to 
flame  the  potassium  color  unobscured  by  that  of  sodium.  It 
is  low  in  chlorids  and  sulfates  and  high  in  carbonates  and  phos- 
phates; about  two- thirds  of  the  phosphates  are  soluble  in  water. 
In  the  ash  of  other  vinegars  a  much  lower  proportion  of  phos- 


VINEGAR  285 

phates  is  soluble  in  water.  The  dilution  of  vinegar  by  natural 
water  will  be  apt  to  reduce  the  soluble  matter  by  the  formation 
of  calcium  and  magnesium  phosphates.  Manufacturers  oc- 
casionally add  potassium  phosphate  to  diluted  cider  vinegars 
to  correct  deficiency. 

Cider  vinegar  is  always  levorotatory.  With  a  200  mm.  tube 
the  reading  will  range  from  o.i  to  4.0  on  the  sugar  scale.  If 
the  direct  reading  is  right  and  the  invert  reading  left,  the  sample 
probably  contains  added  saccharine  matter.  If  the  both  readings 
are  right,  glucose  is  present.  If  the  reading  is  strongly  left,  un- 
fermented  cider  has  probably  been  added  to  increase  the  solids. 

U.  S.  Standard. 
Acetic  acid     not  less  than    ..4        grams  in   100  c.c. 
Apple  solids      "      "       "     ..1.6 
Apple  ash  "      ''       ''     ..0.25        ''       '' 

Water-soluble  ash  from  100  c.c.  must  require  30  c.c.  -—-  acid 
and  contain  not  less  than  o.oio  phosphoric  oxid. 

'Spirit  Vinegar. — This  is  made  by  distilling  a  fermented  mash 
of  grain  so  as  to  obtain  a  very  dilute  alcohol,  technically  called 
"low  wine/'  which  is  converted  without  rectification  or  con- 
centration into  vinegar  by  the  ''quick"  method  above  described. 
Spirit  vinegar  is  often  colored  with  caramel  to  simulate  cider 
or  wine  vinegar.  Pure  spirit  vinegar  on  evaporation  leaves 
but  a  small  amount  of  solids  and  a  trace  of  ash.  The  following 
is  a  summary  of  the  results  obtained  by  A.  W.  Smith  in  the  ex- 
amination of  65  samples  of  spirit  vinegar: 

Average. 

Acetic  acid, 2.87  to  5.99  3.84 

Total  solids, 0.14  "  0.78  0.38 

Ash, o.oi  "  0.15  0.06 

The  ash  had  a  very  slight  alkalinity  and  only  traces  of  phos- 
phates. 

Malt   Vinegar. — This  is  characterized  by  a  comparatively 


286 


FOOD   ANALYSIS 


large  amount  of  nitrogenous  matter.  The  following  table  ex- 
hibits the  usual  composition  as  contrasted  with  vinegar  prepared 
from  glucose  and  sucrose.  The  water  used  in  the  preparation 
of  the  mash  may  have  much  influence  on  the  composition  of 
the  ash.  According  to  Sykes,  various  yeast-foods  containing 
phosphates  are  often  added  to  the  wort  with  a  view  to  stimulate 
the  yeast  and  secure  a  higher  production  of  alcohol. 


Analyst, 

A.W.Smith. 

A.  H.  Allen. 

Character  of 
Vinegar, 

Malt, 
4  Samples. 

Malt, 
4  Samples. 

Chiefly  from  Rice 
Hydrolyzed  by 
Sulfuric  Acid. 

From 
Sugar. 

Per  loo  parts  of  vinegar : 

Per  Cent. 

Grams  per 
100  c.c. 

Grams  per  100  c.c. 

Gms.  per 
100  c.c. 

Acetic  acid, .... 

4.01  to  5.90 

4  86  to  6.61 

5.58 

5- 70 

4.92 

Total  solids,     .    .    . 

1.75  to  2.67 

2.31  to  3  96 

2.98 

2.09 

1.76 

Ash, 

0.20  to  0.28 

0.3410055 
0.091  too  118 

0.30 
0.13 

0.43 

0.278 

**      alkalinity,      . 

0.02  to  0.026 

Phosphoric  oxid,     . 

0.09  to  0.125 

0.057  to  0093 

0.017 

0.024 

0.016 

Nitrogen,     .... 

Not  det. 

0095  to  0.120 

0.104 

0.062 

0.016 

"  Original  solids,"  . 

7.76  to  11.06 

9.60  to  12  73 

II  35 

10.64 

10.02 

JJ .  S.  Standard. 

Acetic  acid     not  less  than   ..4        grams  in   100  c.c. 

Solids  "      ''        "     ..2 

Ash  "      ''       "     ..0.2  ''       ''        " 

The  water  soluble  ash  from  100  c.c.  must  neutralize  not  less 
than  4  c.c.  -^  acid. 

Malt  vinegar  is  often  made  by  acidifying  dilute  alcohol  by 
the  quick  process  and  coloring  the  liquid  by  steeping  in  it  a 
strongly  scorched  malt.  This  form  contains  less  phosphates 
and  solid  matter  than  the  older  form  of  malt  vinegar.  Another 
method  is  the  use  of  so-called  ''malt  acid,"  "  vinegar  extract," 


VINEGAR 


287 


or  ''  vinegar  essence,"  obtained  by  acetifying  dilute  alcohol, 
neutralizing  the  liquid  with  lime  and  distilling  the  resulting 
calcium  acetate  with  sulfuric  acid  by  which  a  product  contain- 
ing from  40  to  90  per  cent,  of  acetic  acid  is  obtained.  The 
acetified  alcohol,  containing  as  much  as  13  per  cent,  of  acetic 
acid,  is  also  sold  under  the  name  "Essig  sprit"  or  "spirit  vine- 
gar."    The  following  analyses  are  due  to  Allen  &  Moor: 


ESSIG 

Sprit.' 


Malt  Acid." 


Acetic  acid, 

Total  solids, 

Ash, 

Alkalinity  of  ash  as  potassium  oxid, 

Phosphorus, 

Nitrogen .    . 

Sulfuric  acid  (free), 


[1. 26 
0.64 
0.06 


Grams  per  loo  c.c. 

88.02 

2.77 

0.15 


Trace 
0.014 


45-4 
12.14 
0.18 

0.017 
0.I13 
0.074 


Commercial  vinegars  are  made  from  these  products  by 
dilution  with  water  and  adding  coloring  and  flavoring  materials. 
According  to  Allen  &  Moor,  it  is  the  practice  of  some  manu- 
facturers to  distil  a  portion  of  the  product,  reserve  the  stronger 
portion  of  the  distillate  for  sale  as  distilled  vinegar,  and  add 
the  weaker  fractions  to  some  of  the  undistilled  article.  Dis- 
tilled malt  vinegar  contains  appreciable  amounts  of  alcohol, 
ethyl  acetate,  furfural,  and  aldehyde,  and  has  a  highly  character- 
istic taste  and  odor. 

^^  Original  Solids. ^^ — Hehner  has  called  attention  to  the 
fact  that  additional  information  as  to  the  nature  of  a  vinegar 
may  be  obtained  by  calculating  the  weight  of  materials  prior 
to  fermentation.  90  parts  of  glucose  should  produce  60  parts 
of  acetic  acid ;  therefore  the  amount  of  acetic  acid  in  the  sample, 


288  FOOD   ANALYSIS 

multiplied  by  1.5  and  added  to  the  solids,  will  give  the  figure 
termed  by  Hehner  "original  solids."  The  loss  of  acetic  acid 
during  fermentation  may,  however,  be  as  much  as  50  per  cent., 
and  the  figure,  therefore,  will  be  only  an  approximation,  but 
it  is  often  instructive.  The  following  table  shows  the  method 
applied  to  the  twenty-two  samples  of  cider  vinegar  given  on 
page  284. 

Milligrams  of 
Milligrams  of        Phosphoric  Oxid 
Solids  X  1.5      Ash  per  100  Grams       per  100  Grams 
Acetic  Acid.         Original  Solid.  of  O.  S. 

Maximum, 14-38  6.09  3.77 

Minimum, 7.63  2.73  1.72 

Average, 9.65  4.11  3.10 

Analytic  Methods. 

Acetic  Acid. — This  may  be  determined  with  sufficient  accu- 
racy by  diluting  5  c.c.  of  the  vinegar  with  50  c.c.  of  water  and 
titrating  with  standard  alkali,  using  phenolphthalein  as  in- 
dicator. 

Total  Solids. — 5  c.c.  of  the  vinegar  are  evaporated  to  con- 
stant weight  in  a  platinum  dish  in  the  water-oven  or  on  a  water- 
bath. 

Ash. — ^A.  W.  Smith  makes  the  following  suggestions  for 
its  examination  and  determination:  10  grams  of  the  sample 
should  be  evaporated  and  ashed  by  small  portions  (not  more 
than  10  c.c.)  at  not  above  a  low  red  heat.  The  residue  is  dis- 
solved and  tested  qualitatively  by  the  flame-test  and  for  chlorids 
and  sulfates.  Unless  the  latter  are  present  in  excess  of  the 
amount  usually  found  in  pure  samples,  they  need  not  be  de- 
termined quantitatively.  For  alkalinity  of  the  ash  and  pro- 
portion of  phosphates,  25  grams  of  the  sample  are  dried  and 
burned,  the  ash  extracted  repeatedly  with  hot  water,,  pouring 
the  solution  through  an  ashless  filter  upon  which  the  insoluble 
portion  is  collected.  The  filtrates  are  mixed  and  titrated  with 
standard  acid,  methyl  orange  being  generally  used  as  indicator. 
Nitric  acid  is  added  to  the  liquid  and  the  phosphates  determined 


UNIVERSITY 

OF 
VINEGAR  289 

by  the  ammonium  molybdate  method.  The  filter  is  dried, 
burned,  weighed,  repeatedly  extracted  with  hot  dilute  nitric 
acid,  and  the  phosphate  in  the  solution  also  determined. 

Nitrogen. — 50  c.c.  are  evaporated  to  small  bulk  and  treated 
by  the  Kjeldahl-Gunning  method. 

Mineral  Acid. — If  the  ash  be  alkaline,  no  mineral  acid  can 
have  been  present  except  nitric  acid;  but  if  neutral,  Ashby's 
test  should  be  applied.  A  drop  of  solution  of  logwood  ex- 
tract in  water  (0.5  gram  to  100  c.c.)  is  dried  on  a  porcelain 
plate,  a  drop  of  the  vinegar  added,  and  again  dried.  The 
residue  from  pure  vinegar  will  be  yellow,  but  will  be  red  if  min- 
eral acid  be  present.  If  the  proportion  of  acid  be  small,  the 
red  color  is  destroyed  by  the  addition  of  water,  but  is  restored 
on  evaporation,  except  in  the  case  of  nitric  acid,  which  does 
not  appear  to  be  used  for  adulteration. 

The  amount  of  free  mineral  acid  is  determined  by  Heh- 
ner's  method  as  follows:  50  c.c.  of  the  sample  are  mixed  with 
a  measured  amount  of  decinormal  alkali,  preferably  less  than 
sufficient  to  neutralize  all  the  acid,  but  rather  more  than  suf- 
ficient to  neutralize  the  mineral  and  fixed  organic  acids  present. 
The  mixture  is  evaporated  to  dryness,  ashed  at  a  low  red  heat, 
and  titrated  with  standard  acid.  In  the  absence  of  mineral 
acid,  the  ash  will  have  an  alkalinity  equal  to  the  standard  alkali 
added.  Any  deficiency  in  alkalinity  will  be  due  to  the  presence 
of  mineral  acid. 

Vinegar  containing  sulfuric  acid  usually  leaves  a  charred 
residue  on  evaporation  in  the  water-bath.  For  samples  con- 
taining but  little  organic  solids  the  test  may  be  made  applicable 
by  adding  a  little  sucrose.  Sulfuric  acid  as  distinguished  from 
sulfates  may  be  determined  by  Allen's  method  as  follows:  100 
c.c.  of  the  vinegar  are  evaporated  to  10  c.c,  and  to  the  cold 
concentrated  liquid  50  c.c.  of  alcohol  are  added.  Sulfates  are 
precipitated,  but  sulfuric  acid  remains  in  solution.  The  filtered 
liquid  is  diluted,  the  alcohol  boiled  off,  and  the  sulfuric  acid 
26 


290  FOOD   ANALYSIS 

determined  by  precipitation  with  barium  chlorid.  In  vinegar 
free  from  chlorids  this  process  gives  results  in  accordance  with 
Hehner's  process,  but  when  chlorids  are  present  the  mineral 
acid  found  is  deficient  by  the  amount  required  to  decompose 
the  chlorids.  This  difficulty  may  be  overcome  by  treating 
the  sample  with  excess  of  solution  of  silver  sulfate  before  evap- 
oration, by  which  any  free  hydrochloric  acid  will  also  be  esti- 
mated as  sulfuric  acid. 

Caramel  may  be  detected  by  the  method  given  on  page  130. 

Potassium  acid  tartrate,  which  occurs  in  true  wine  vinegar, 
may  be  detected  by  dissolving  the  solid  residue  in  a  little  water, 
adding  alcohol  and  stirring  the  mixture  with  a  glass  rod;  the 
tartrate  will  be  deposited  in  crystals  along  the  lines  touched  by 
the  rods. 

Malic  acid  is  always  present  in  cider  vinegar,  and  is  indicated 
by  a  flocculent  precipitate  with  lead  acetate,  which  settles 
quickly.  Other  vegetable  acids  may  give  such  a  precipitate. 
Leach ^^  distinguishes  malic  acid  as  follows: 

A  few  drops  of  a  10%  solution  of  calcium  chlorid  are  added  to 
10  c.c.  of  vinegar  and  the  liquid  made  slightly  alkaline  with 
ammonium  hydroxid.  Any  precipitate  is  removed  by  filtration, 
30  c.c.  of  alcohol  added  to  the  filtrate  and  heated  to  boiling. 
Calcium  malate  will  separate,  which  settles  quickly,  but  pre- 
cipitates may  also  be  formed  in  vinegar  containing  dextrin. 
The  precipitate  is  collected  on  a  filter,  washed  with  a  little  alcohol, 
dissolved  in  strong  nitric  acid  in  a  porcelain  dish,  and  evaporated 
to  dryness  on  the  water-bath.  The  residue  is  boiled  with 
sodium  carbonate,  filtered,  the  filtrate  acidified  with  acetic 
acid,  carbon  dioxid  expelled  by  boiling  and  calcium  sulfate 
solution  added.  Calcium  oxalate  will  be  thrown  down  if  malic 
acid  is  present  in  the  sample.  The  characteristic  octahedral 
crystals  can  sometimes  be  recognized  under  high  power. 

Poisonous  metals  may  be  encountered,  especially  in  vinegar 
containing  free  mineral  acid.     Arsenic  may  be  detected  by 


SPICES  291 

Reinsch's  test  (p.  60).  Lead,  copper,  tin,  and  zinc  may  be  tested 
for  directly  in  light-colored  vinegars,  but  in  most  cases  it  will 
be  necessary  to  examine  the  residue  from  a  large  amount  of  the 
sample  in  accordance  with  the  methods  given  on  page  581. 

SPICES 

Several  processes  applicable  especially  to,  or  modified  for, 
the  examination  of  spices  require  description. 

Moisture. — This  determination  cannot  be  made  in  the  usual 
way  on  account  of  the  loss  of  volatile  oil.  Richardson  and  Mc- 
Gill  have  devised  methods  for  the  purpose. 

Richardson's  method  is  to  dry  2  grams  in  an  air-oven  at  110° 
until  the  weight  is  constant,  which  generally  requires  twelve 
hours.  The  loss  is  moisture  and  volatile  oil.  The  latter  is 
determined  from  the  loss  in  heating  the  total  ether  extract,  as 
noted  below,  and,  being  deducted  from  the  total  loss  on  the  oven- 
drying,  leaves  the  moisture.  Richardson  found  the  data  thus 
obtained  to  be  satisfactory. 

McGill  prefers  to  dry  the  weighed  material  in  vacuum  over 
pure,  colorless,  sulfuric  acid.  The  moisture  is  first  given  off, 
and  by  watching  the  acid,  the  beginning  of  discoloration  due 
to  absorption  of  volatile  oil  and  its  carbonization  by  the  acid 
will  indicate  the  completion  of  the  drying,  and  the  sample  can 
be  weighed.     About  24  hours  are  required  for  this. 

Ether- extract. — The  ether-extract  of  spices,  consisting  of 
bodies  volatile  at  widely  different  temperatures,  must  be  dried 
in  a  definite  manner  to  give  comparable  results.  The  following 
is  the  usual  routine:  When  the  extraction  is  completed,  the 
ether  is  mostly  distilled  off  (see  page  42)  and  the  remainder 
allowed  to  evaporate  spontaneously  at  room-temperature. 
The  container  is  placed  in  a  desiccator  over  strong  sulfuric 
acid  for  twelve  hours,  after  which  it  is  weighed;  the  weight  is 
''total  ether  extract."  The  container  is  brought  slowly  up  to 
100°,  and  then  heated  at  110°  until  weight  is  constant.     This 


292  FOOD   ANALYSIS 

weight  is  "  non- volatile  ether  extract."  The  difference  between 
the  two  weights  is  volatile  oil. 

Alcohol  extract. — Winton,  Ogden  &  Mitchell  applied  with 
advantage  the  method  of  extraction  noted  on  page  42,  using  2 
grams  of  the  powdered  material  and  100  c.c.  of  alcohol.  The 
liquid  is  filtered  through  a  dry  filter  and  a  measured  portion 
(50  c.c,  equivalent  to  i  gram  of  material  is  convenient)  evapo- 
rated and  the  residue  weighed. 

Tannins. — Determination  of  tannin  is  sometimes  necessary. 
This  is  done  most  easily  by  Richardson's  modification  of  the 
standard  indigo  method,  which  depends  on  the  oxidation  of 
the  tannin  by  permanganate.^^     The  solutions  used  are: 

Potassium  permanganate. — 1.333  grams  pure  substance  is 
dissolved  in  water  and  made  up  to  1000  c.c.  The  value  of 
this  in  terms  of  oxalic  acid  should  be  determined  as  follows: 
10  c.c.  of  decinormal  oxalic  acid  (6.3  gra.ms  of  crytallized  oxalic 
acid  in  1000  c.c.)  are  diluted  with  water  to  500  c.c,  heated  to  60°, 
20  c.c  of  dilute  sulfuric  acid  (i  :  3)  added  and  the  permanganate 
solution  added  slowly  with  constant  stirring  until  the  pink  tint 
is  no  longer  destroyed  promptly.  The  value  of  the  permanga- 
nate in  terms  of  the  indigotate  solution  should  also  be  determined 
by  titrating  a  mixture  of  750  c.c  of  water  and  20  c.c.  of  in- 
digotate solution  until  a  golden  yellow  liquid  is  produced. 

Indigo  solution. — 6  grams  of  pure  sodium  sulfindigotate  are 
dissolved  in  50  c.c.  of  water,  by  the  aid  of  heat,  cooled,  50  c.c 
of  strong  sulfuric  acid  added,  and  the  solution  made  up  to  a 
liter. 

Two  grams  of  the  material  are  extracted  for  a  considerable 
time  with  anhydrous  ether  and  then  boiled  for  two  hours  with 
300  c.c.  of  water,  cooled,  made  up  to  500  c.c  and  filtered. 
25  c.c.  of  the  filtrate  are  transferred  to  a  1200  c.c.  flask,  750  c.c 
of  water  added  and  20  c.c.  of  indigotate  solution,  and  the  mix- 
ture titrated  with  standard  permanganate,  until  a  golden 
yellow  solution  is  produced. 


PEPPER  293 

The  amount  of  permanganate  required  for  the  indigotate 
solution  is  deducted  from  the  total  permanganate  used,  and  the 
value  of  the  remainder  is  calculated  to  oxalic  acid,  i  c.c.  of 
oxalic  acid  is  equivalent  to  0.0008  of  absorbed  oxygen  or  0.00623 
of  tannin,  expressed  as  quercitannic  acid. 

PEPPER 

Pepper  is  the  fruit  of  the  Piper  nigrum  L.,  of  the  order  Pi- 
peracecB.  Black  pepper  is  the  unripe  fruit,  dried  in  the  sun; 
white  pepper  is  obtained  by  soaking  the  ripe  fruit  in  water  and 
removing  the  husks  by  friction. 

Pepper  contains  alkaloid,  piperin,  an  acrid  resin,  a  volatile 
oil,  starch,  a  small  amount  of  nitrates,  and  the  usual  plant 
constituents. 

Piperin. — The  proportion  of  this  in  pepper  ranges  between 
4  and  8  per  cent.  It  forms  colorless,  four- sided,  monoclinic 
prisms,  melting  at  128°  and  decomposing  at  a  slightly  higher 
temperature.  It  is  insoluble  in  cold  and  but  slightly  soluble 
in  hot  water,  dissolves  in  alcohol,  forming  a  neutral  solution 
of  pungent  taste,  is  freely  soluble  in  chloroform,  benzene,  and 
petroleum  spirit,  but  less  so  in  ether.  It  is  extracted  even  from 
acid  solutions  by  chloroform.  Boiled  with  strong  alkali,  it  is 
converted  into  piperidin  and  a  piperate. 

Piperidin  is  a  colorless  liquid  with  an  odor  recalling  both 
ammonium  hydroxid  and  pepper.  It  boils  at  106°,  is  strongly 
basic,  and  may  be  estimated  by  titration  with  standard  acid, 
using  methyl-orange  as  indicator.  Small  proportions  are 
found  in  pepper.  According  to  Johnstone,  black  pepper  con- 
tains from  0.39  to  0.77  per  cent.,  and  white  pepper  from  0.21 
to  0.42  per  cent. 

The  resin  of  pepper  is  dark  green  and  has  a  hot  pungent 
taste.  It  is  soluble  in  alcohol,  ether,  and  sodium  hydroxid 
solution,  and  in  water  in  the  presence  of  the  other  constituents 
of  pepper. 


294 


FOOD   ANALYSIS 


The  volatile  oil  of  pepper  is  a  terpene  having  a  boiling-point 
of  167°-!  70°.  It  has  the  smell  of  pepper,  but  not  its  pungency. 
It  is  usually  present  to  the  extent  of  about  i  per  cent. 


am 


Fig.  49. 
A,  Starch  granules  (X  600);  am,  cell  containing  starch;  p,  parenchyma  with 
resin;  ft/,  bast  fibers;  hp,  bast  parenchyma;  sp,  spiral  vessels;  ep,  epider- 
mis; ast,  stony  parenchyma;  as  and  is,  seed  membrane  in  two  layers; 
ist,  inner  stone-cell  layer  with  horseshoe-shaped  cells.  The  structures  ist, 
as,  and  is  are  more  characteristic,  especially  the  two  latter,  consisting  of  a 
light  and  a  dark  layer.     All  (except  ^,  as  above)  X  160. 


Starch. — Pepper-starch  is  in  minute  granules,  not  more  than 
0.005  mm.  in  diameter,  round  or  polygonal,  and  often  in  clusters. 
Under  a  high  power  they  show  a  central  nucleus  or  vesicle. 


7.0 

per 

cent 

2.0 

a 

(( 

I5.0 

a 

u 

25.0 

a 

a 

PEPPER  295 

U.  S.  Standard,  Blatk  pepper. — 
Ash  not  more  than 

Ash  insol.  in  hy- 
drochloric acid    "        " 
Crude  fiber  "       " 

Starch  not  less  than 

Non- volatile  ether- 
extract  "       "        ''     ..  6.0      "        '' 
The  non-volatile  ether-extract  must  contain  not  less  than 
3.25  per  cent,  of  nitrogen. 

U.  S.  Standard,  White  pepper. — 
Ash  not  more  than   . .  4.0   per  cent. 

Ash  insol.  in  hy- 
drochloric acid   ''       "        ''     -  -  0.5      "       '' 
Crude  fiber  ''       ''        *'     ..  5.0      ''       '' 

Starch  not  less  thcin    ..50.0      "       " 

Non- volatile  ether- 
extract  *'      ''       "     ..  6.0      "       '' 
The  non-volatile  ether-extract  must  contain  not  less  than 
4.0  per  cent,  of  nitrogen. 

The  microscopic  appearance  of  ground  pepper  is  shown  in 
figure  48,  from  a  drawing  by  Moeller.*^ 

Adulteration  of  Pepper. — The  following  are  some  of  the 
adulterants  which  may  be  looked  for  in  pepper:  Pepper  husks, 
long-pepper,  wheat,  buckwheat,  cayenne  pepper,  mustard 
husks,  ground  olive  stones  (poivrette  or  pepperette),  almond 
and  cocoanut  shells  (often  roasted  or  charred),  Egyptian  corn, 
spent  ginger,  and  coriander  seed.  Of  mineral  additions,  sand, 
clay,  brick  dust,  chalk,  barium  sulfate,  and  lead  chromate  are 
known  to  have  been  used. 

In  the.  examination  of  pepper,  considerable  reliance  must 
be  placed  upon  the  microscopic  characters.  Numerous  chem- 
ical examinations  have  been  made,  but  the  results  in  many 


296  FOOD    ANALYSIS 

cases  have  been  conflicting,  and  the  uncertainty  has  been  in- 
creased by  the  fact  that,  until  recently,  hardly  any  two  workers 
have  employed  the  same  methods. 

Analytic  Methods.  Data.— These  are  directed  to  the  de- 
termination of  starch,  ash,  insoluble  ash,  non-volatile  ether- 
extract,  crude  fiber  and  total  nitrogen.  The  alcohol  and  water- 
extract  have  been  shown  to  be  valueless  in  this  connection. 

Moisture. — This  is  determined  as  on  page  291. 

Ether-extract. — This  is  termed  non-volatile  extract,  because 
it  is  weighed  after  heating  on  the  water-bath  in  order  to  drive 
out  the  solvent.  It  contains  piperin,  resin,  and  some  volatile 
oil,  and  for  the  purpose  of  detecting  adulteration  is  more 
convenient  and  satisfactory  than  the  determination  of  piperin 
alone.  If  desired,  the  piperin  may  be  determined  as  follows: 
The  mixture  of  piperin  and  resin  obtained  by  extraction  is 
treated  with  sodium  hydroxid,  by  which  the  resin  is  dissolved; 
the  residue  is  dissolved  in  alcohol,  the  solution  filtered,  evapo- 
rated, and  the  residue  (piperin)  weighed.  Another  method  is 
to  mix  a  weighed  portion  of  the  powdered  pepper  with  slaked 
lime  and  water,  dry  at  100°,  and  thoroughly  extract  with  ether. 
The  residue  left  on  the  evaporation  of  the  ether  is  purified  by 
solution  in  alcohol,  filtration,  and  crystallization. 

The  proportion  of  ether-extract  is  usually  not  less  than  7 
per  cent.,  but  may  fall  below  this  figure  even  in  pure  peppers. 
(See  standard,  page  295.) 

Nitrogen. — Determination  of  total  nitrogen  by  the  Kjeldahl- 
Arnold  method  (see  page  36)  is  now  substituted  for  the  piperin 
determination  in  the  routine  examination  of  pepper. 

Crude  Fiber. — This  should  be  determined  on  the  ether- 
extracted  material  as  described  on  page  38.  Richardson's 
figures  and  those  of  Winton  in  the  following  table  were  ob- 
tained in  this  way.  Those  of  Stokes  were  made  without 
previous  exhaustion  with  ether.  Heisch  reported  "cellulose," 
but  the  method  of  determination  is  not  stated. 


PEPPER  •  297 

Analyst, Richardson.  Winton.  Stokes.  Heisch. 

Black  pepper, S.otoii.o  8.571015.41  21.01026.3  11.51027.8 

White  pepper, 4.1  to   8.0  "3-32  to   4.16  12.71013.8  3-4  to    6.7 

Long-pepper, 7.38  20.01022.3  1.141012.9 

Pepper     shells     or 

dust, 22.8 

Olive  stones, •         ..  62.21064.2  61.91068,8 

Ash. — In  unadulterated  black  pepper  the  proportion  of  ash 
rarely  exceeds  5  per  cent.;  over  7.0  per  cent,  may  be  taken  as 
evidence  of  adulteration.  The  ash  of  v^hite  pepper  should 
not  exceed  4.0  per  cent.  If  long-pepper  be  present,  the  ash 
is  apt  to  be  high,  for  the  reason  given  below.  Stock  has  pub- 
lished the  following  determinations  in  genuine  peppers: 

Tellicherry.  Siam.  Lampong.  Penang. 

Ash, 1.05  1.45               2.20  2.75 

Fiber, 4.86  4.43              4.90  5.06 

Calc.  carb.  in  pepper,  .. .   0.58  0.62              0.81  1.67 

"         '*     "ash, 55-20  42.70  36.80  60.70 

Tellicherry  Pepper.  Unhulled.  Hulled. 

Total  ash, 4.02  i  .64 

Fiber, 10.40  6.80 

Ratio  of  calcium  (as  carbonate)  to  ash, 27.30  62.00 

It  is  thus  seen  that  calcium  compounds  are  more  abundant 
in  pepper.  Excess  of  hulls  results  in  a  lowering  of  this  ratio, 
but  the  proportion  may  be  altered  in  samples  that  have  been 
bleached  or  faced  with  mineral  matter.  Stock  considers  that 
in  pure  pepper  the  proportion  of  calcium  carbonate  to  total 
ash  is  never  greater  than  60  per  cent. 

It  is  advisable  to  shake  up  a  portion  of  the  pepper-sample 
with  chloroform  in  a  tapped  separator.  The  heavier  mineral 
additions  will  sink,  along  with  more  or  less  husk,  and  may  be 
removed  by  means  of  the  tap  and  examined  with  the  micro- 
scope and  chemically.  In  this  way  it  may  be  possible  to  dis- 
tinguish between  added  mineral  matter  and  that  naturally 
present. 

Winton  has  called  attention  to  the  fact  that  in  the  ether- 


298  FOOD   ANALYSIS 

extract  of  pure  pepper  the  piperin  invariably  crystallizes  out 
from  the  resin  on  cooling,  but  that  when  pepper  is  adulterated 
with  material  containing  fat  or  oil,  the  latter  may  conceal  the 
crystals  or  prevent  their  formation.  Absence  of  piperin  crystals 
is  regarded  as  positive  evidence  of  adulteration.  If  the  fat  or 
oil  introduced  by  the  adulterant  increases  the  weight  of  the 
extract  to  the  amount  which  is  found  in  pure  pepper,  a  deter- 
mination of  the  nitrogen  in  the  extract  will  often  disclose  the 
adulteration. 

Starch. — Many  determinations  have  been  made,  but  the 
methods  used  have  been  faulty  and  the  indications  often 
unsatisfactory.  Heisch  boiled  the  pepper  for  three  hours 
with  10  per  cent,  hydrochloric  acid  and  measured  the  optic 
activity  of  the  resulting  liquid.  The  gum  and  other  soluble 
matters  were  found  to  cause  a  rotation  equivalent  to  about  i 
per  cent,  of  starch.  Lenz  extracted  the  pepper  with  water, 
boiled  the  residue  with  hydrochloric  acid,  and  determined  the 
reducing  sugar.  All  the  samples  of  pepper  examined  gave 
a  reducing  sugar  equivalent  of  over  50  per  cent.,  while  the 
adulterants,  except  those  containing  starch,  gave  under  30  per 
cent.  Rottger,  however,  found  Lampong  pepper  to  give  a 
" reducing- sugar  equivalent"  of  only  41.7  per  cent.  Richard- 
son found  the  starch  in  5  samples  of  black  pepper  to  vary  be- 
tween 34  and  38  per  cent,  of  the  dry  ash-free  material.  In  two 
samples  of  white  pepper  the  figures  were  about  40  and  43  per 
cent,  respectively. 

Substances  other  than  starch  are  converted  into  sugar  by 
the  above  processes.  The  U.  S.  standard  for  starch  in  pepper  is 
based  on  the  diastase  method  given  on  page  93. 

Ground  olive-stones,  termed  "poivrette"  and  "pepperette," 
have  been  much  used  to  adulterate  pepper.  J.  Campbell 
Brown,  who  first  called  attention  to  this  use,  has  given  the  re- 
sults of  analysis  of  samples: 


PEPPER  299 

Ash.  Fiber. 

White  pepperette, i  .33  48.48 

Black  pepperette, 2.47  47-69 

Ground  olive-stones, 1.61  45-38 

Ground  almond-shells, 2.05  51-68 

None  of  the  samples  contained  starch. 

Poivrette  is  a  pale  buff  or  cream-colored  powder,  which  can- 
not be  distinguished  from  the  materials  of  genuine  pepper  by 


Fig.  50. 
a,  Cells  associated  with  the  vascular  bundles,  also  some  stone-cells;  i,  inner 
layer  of  hard  cells,  with  endothelium  en;  p,  cells  from  the  fleshy  portion 
of  the  fruit;  ep,  epidermis  of  the  seed  wall,  with  brown  parenchyma  showing 
through  it;  ea,  exterior  layer  of  the  endosperm.  Some  spiral  vessels  are 
also  .shown.    X  160. 

simple  inspection.  The  particles  are,  however,  tough  and  hard, 
and  may  be  sometimes  detected  by  crushing  the  sample  between 
the  teeth.  Under  the  microscope  the  powder  shows  dense 
ligneous  cells,  some  entire,  with  linear  air-spaces,  others  torn 
and  indistinct.  Figure  50  shows  some  structures  of  olive  seed 
and  figure  51  some  structures  of  nut-shells.  Both  are  from 
Moeller's  work."*® 


300 


FOOD   ANALYSIS 


By  treatment  with  dilute  sodium  hydroxid  solution  and 
washing  by  decantation  poivrette  will  appear  yellow  and  pepper 
husk  dark.  Although  poivrette  contains  no  starch,  it  yields  a 
reducing  substance  on  boiling  with  hydrochloric  acid. 

Bleached  pepper  husks  are  distinguished  from  poivrette  by 
the  microscopic  appearance.  An  incomplete  separation  of 
poivrette  may  be  effected  by  shaking  the  sample  in  a  mixture 
of  equal  parts  of  glycerol  and  water,  in  which  poivrette  sinks 
more  rapidly. 

Several  color  tests  have  been  proposed.  Gillet  advises  the 
use  of  a  7  per  cent,  alcoholic  solution  of  iodin,  which  stains 

pepper  brown  and  poivrette 
bright  yellow.  Chevreau  uses  a 
solution  of  anilin  in  three  parts 
of  acetic  acid.  Pure  pepper  is 
almost  unaffected,  but  poivrette 
becomes  bright  yellow,  and  under 
the  microscope  the  stone  cells 
exhibit  a  pure  gamboge  yellow. 
Pabst  uses  a  solution  of  di- 
methyl-1-4-diamidobenzene,  pre- 
pared as  follows :  i  gram  of  com- 
mercial dimethylanilin  is  mixed 
in  a  porcelain  dish  with  2  grams 
of  strong  pure  hydrochloric  acid,  10  grams  of  broken  ice  are 
added,  and,  little  by  little,  with  constant  stirring,  a  solution  of  0.7 
gram  of  sodium  nitrate  in  10  c.c.  of  water.  After  half  an  hour  3 
to  4  grams  of  hydrochloric  acid  and  2  grams  of  tin-foil  are  added. 
The  reduction  is  allowed  to  go  on  for  an  hour,  when  the  tin  in 
solution  is  precipitated  by  means  of  zinc.  The  decanted  and 
filtered  liquid  is  treated  with  a  slight  excess  of  sodium  carbonate 
and  the  precipitate  thus  produced  redissolved  by  the  addition 
of  acetic  acid,  i  gram  of  sodium  acid  sulfite  is  added  and  the 
liquid  diluted  to  200  c.c.     In  testing  pepper,  2  c.c.  of  the  solution 


Fig.  51. 
Exterior  layer;    m,  intermediate 
layer;  ^,  inner  layer. 


PEPPER  301 

are  placed  in  a  shallow  dish  and  a  pinch  of  the  pepper  sprinkled 
into  it.  In  a  few  minutes  the  particles  of  olive  stones  become 
a  brilliant  carmine,  while  the  grains  of  pepper  remain  unaltered 
or  become  only  faintly  pink.  If  some  water  be  now  added,  the 
heavy  particles  of  olive  stones  fall  to  the  bottom  and  are  de- 
tected with  ease.  Ground  nut- shells  are  colored  in  the  same 
way. 

The  phloroglucol-hydrochloric  acid  solution  (page  26)  pro- 
duces with  olive  stones  and  nut-shells  a  deep  crimson  stain 
which  is  very  characteristic.  The  action  is  obtained  promptly 
on  moistening  the  sample  with  a  few  drops  of  the  reagent. 
Under  a  magnifying  power  of  about  200  diameters  the  stained 
stone-cells  are  clearly  seen. 

Dhoura  Corn. — This  is  a  variety  of  sorghum,  known  in 
England  as  Turkish  millet  and  in  America  as  Egyptian  corn. 
Brown  called  attention  to  its  use  in  pepper,  and  gave  the  fol- 
lowing analyses  and  description.  The  two  samples  contained 
II  per  cent,  of  moisture;  the  figures  are  percentages  of  the  dry 
material : 

Ash, 1.31  1.69 

Starch, 73 .20  73.20 

Cellulose, 2.56  419 

Ether-extract, 1 1 .10  7.30 

Nitrogen, 1.82  1.78 

The  material  designated  "cellulose"  is  probably  crude  fiber, 
obtained  by  using  stronger  solutions  than  directed  in  the  A.  O. 
A.  C.  method.  The  grain  is  roundish,  oval,  or  somewhat 
flattened,  2  to  5  mm.  in  diameter.  The  body  is  white  and  con- 
sists mainly  of  roundish  starch  granules,  the  general  characters 
of  which  are  given  on  page  90. 

Coriander  Seed. — Hanausek  has  called  attention  to  the  adul- 
teration of  pepper  with  ground  coriander  seed.  The  following 
peculiarities  were  observed  under  the  microscope :  (a)  bundles 
of  corrugated  bent  fibrous  cells;    {h)  coarse  parenchyma  over- 


302  FOOD   ANALYSIS 

laid  with  narrow  cells  of  a  yellow  color,  with  parallel  walls; 
(c)  colorless  cellular  parenchyma  firm  in  the  walls  and  in- 
closing numerous  crystalline  rosettes  and  granules.  The  last 
two  peculiarities  were  recognized  as  characteristic  of  a  fruit  of 
the  order  Umbellijerce,  the  bundles  of  fibers,  as  well  as  the  ab- 
sence of  vittae  (oil  cavities),  pointing  to  coriander. 

Cayenne  pepper  is  often  added  to  adulterated  pepper  to  restore 
pungency.  It  may  be  detected  by  the  characteristic  irritating 
vapor  produced  on  heating  some  of  the  separated  red  particles. 
An  alcoholic  or  ethereal  solution  also  gives  off  such  vapors. 

LONG    PEPPER 

Long  pepper  is  the  fruit  of  at  least  two  species,  formerly  in- 
cluded under  the  genus  Piper  L.  (Piperacece),  now  included 
under  the  genus  Chavica  Miq.  It  consists  of  long,  nearly 
cylindrical  spikes,  covered  with  closely  packed  coalesced  fruit, 
which  are  picked  unripe.  The  Chavica  officinarum,  from  Java, 
consists  of  spikes  about  4  to  6  cm.  in  length.  The  spikes  of 
the  Chavica  Roxburghii  are  about  half  as  long.  The  latter  is 
the  more  common  form. 

Long  pepper  usually  contains  a  considerable  proportion  of 
extraneous  matter  (clay  and  soil)  embedded  in  the  crevices 
and  irregularities  of  the  fruit.  The  outer  husk  and  central 
woody  stem  are  not  so  readily  removed  as  in  the  case  of  black 
pepper,  so  that  the  proportion  of  woody  fiber  is  larger  than 
in  ground  black  pepper  of  the  same  shade,  but  not  so  high  as  in 
most  husky  black  pepper.  Long  pepper  contains  less  piperin 
than  most  black  pepper,  and  has  a  disagreeable  odor  and  flavor; 
in  the  ground  state,  it  is  not  a  recognized  article  of  commerce. 
It  is  used  whole  in  pickles  and  has  been  employed  to  adulterate 
ground  black  and  white  pepper.  The  following  are  some  re- 
sults of  analysis  of  long  pepper: 


PEPPER  303 


Total 
Ash. 

Ash  Insol. 
Acid. 

Starch  and 
Matter  Con- 
vertible 
INTO  Sugar. 

Fiber. 

Ether- 
extract. 

Nitrogen. 

Analyst. 

8.91 

1.2 

44.04 

15-7 

5-5 

2.1 

Brown. 

8.98 

i.i 

49-34 

10.5 

4.9 

2.0 

" 

9.61 

1-5 

44.61 

10.7 

8.6 

.  2.3 

" 

8.10 

7.28 

7.24 

Winton 

Winton's  figures  were  obtained  by  the  A.  O.  A.  C.  methods. 

According  to  Brown,  long  pepper  may  be  detected  in  ground 
pepper  by  the  following  characters:  The  presence  of  any 
considerable  quantity  of  long  pepper  will  impart  to  the  ground 
material  its  peculiar  slaty  color;  but  this  is  made  much  lighter 
by  the  practice  of  sifting  out  much  of  the  darker  or  husky  por- 
tions of  the  long  pepper  before  mixing.  Bleaching  is  also 
resorted  to.  The  odor  of  the  mixture  when  warmed  is  un- 
mistakable, even  if  the  quantity  is  comparatively  moderate. 
The  ether-  or  alcohol-extract  also,  if  the  solvent  has  been  evap- 
orated at  a  low  temperature,  yields  the  characteristic  odor 
when  warmed. 

Long  pepper  often  introduces  a  considerable  amount  of 
mineral  matter,  especially  sand  and  other  material  insoluble 
in  acid.  This  fact  is  important  in  examining  white  peppers,  in 
which  the  proportion  of  ash  is  low.  Long  pepper,  even  if  the 
husk  particles  have  been  sifted  out,  will  still  introduce  some 
sand,  as  well  as  spent  bleach,  if  an  attempt  has  been  made  to 
bleach  it. 

The  woody  matter  in  ground  long-pepper  is  always  con- 
siderable. If  the  sample  be  spread  out  in  a  smooth  thin  layer 
on  paper  by  means  of  an  ivory  paper-knife,  pieces  of  fluffy 
woody  fiber  will  be  detected,  especially  if  the  smooth  thin  layer 
be  tapped  from  below.  These  pieces  come  from  the  central 
part  of  the  indurated  catkin,  which  cannot  be  completely  ground 
fine,  and  are  very  characteristic. 

Some  of  the  starch  granules  of  long  pepper  are  of  larger 
size  (0.005  mm.)  than  those  of  ordinary  pepper,  which  are 
but  slightly  smaller  than  those  of  rice. 


304  FOOD   ANALYSIS 

According  to  Stokes,  long  pepper  may  be  detected  by  placing 
a  small  portion  on  a  microscope  slide,  adding  a  drop  of  glycerol, 
and  examining  under  a  power  of  about  50  diameters  and  crossed 
nicols.  If  ordinary  pepper  only  be  present,  the  field  will  re- 
main dark,  but  long  pepper  presents  a  luminous  white  appear- 
ance. The  same  is  true  of  particles-  of  rice.  By  treating  the 
finely  powdered  material  for  24  hours  with  chloral  solution,  it 
is  rendered  more  transparent,  and  more  satisfactory  examina- 
tion may  be  made.  Rimmington  recommends  shaking  the 
material  several  times,  first  with  alcohol  and  then  with  water 
in  a  test-tube,  and  allowing  to  subside.  Several  strata  are 
usually  formed,  the  uppermost  of  which  should  be  removed  by 
means  of  a  pipet  and  examined  with  a  power  of  250  diameters. 
Every  particle  will  be  seen  clear  and  well  defined  and  foreign 
bodies  easily  recognized. 

CAYENNE  PEPPER 

Cayenne  pepper,  the  ground  pods  of  several  species  of 
Capsicum,  is  a  brick-red  powder  of  intensely  pungent  taste  and 
characteristic  odor.  When  heated,  an  acrid,  irritating  vapor 
is  given  off,  the  production  of  which  may  be  utilized  as  a  test 
for  the  pepper,  even  on  a  minute  quantity  of  the  material.  This 
action  is  due  to  a  crystalline  body  that  melts  at  59°  and 
volatilizes  at  115°.  It  may  be  obtained  by  extracting  the  pepper 
with  petroleum  spirit,  evaporating,  and  treating  the  dry  extract 
with  a  dilute  solution  of  potassium  hydroxid.  On  saturating  the 
liquid  with  carbon  dioxid  the  substance  is  precipitated  in  small 
crystals,  readily  soluble  in  alcohol,  ether,  amyl  alcohol,  and  fixed 
oils,  but  less  so  in  petroleum  spirit  and  carbon  disulfid.  It  is 
usually  more  abundant  in  the  pods  than  in  the  seeds,  in  which 
it  exists  dissolved  in  the  fixed  oil.  It  was  discovered  by  Thresh, 
who  found  also  a  small  quantity  of  an  alkaloid  resembling  conin. 
The  coloring-matter  of  cayenne  pepper  is  but  slightly  soluble 
in  alcohol,  but  dissolves  readily  in  oils,  carbon  disulfid,  petro- 


CAYENNE  PEPPER 


305 


leum  spirit,  ether,  and  chloroform.  The  odor  is  due,  at  least 
in  part,  to  the  presence  of  a  minute  quantity  of  volatile  oil. 

The  following  are  some  published  analyses : 

Fruit  of  Capsicum  annuum,  grown  in  Hungary  (Richard- 
son): 

Whole 
Seed.  Pod.  Fruit. 

Water  at  100°, 8.12  14.75  ii-94 

Albuminoids, 18.31  10.69  13-88 

Ether-extract, 28.54  5.48  15.26 

Nitrogen -free  matter  by  difference, 24.33  38-73  3263 

Crude  fiber, i7-5o  23.73  21.09 

Ash, 3.20  6.62  5.20 

Nitrogen, 2.93  1.71  2.22 

Average  of  several  analyses  by  Blyth: 

Water-extract, 32.10 

Alcohol-extract, 25.79 

Benzene-extract, 20.00 

Ether-extract, io-73 

Nitrogen, 2.04 

Ash, 5.69 

Two  analyses  by  Richardson: 

Ether-  Album-  Nitro- 

Water.        Ash.         extract.         Fiber.         inoids.  gen. 

Zanzibar, 2.35  9.06  26.99  16.88  13-13  2.10 

Crosse  and  Black  well, .  .5.74  5.24  i7-9o  18.10  11.20  1.79 

Adulteration. — The  adulterant  most  commonly  added  to 
cayenne  pepper  is  rice  flour  or  similar  material.  Brick  dust 
is  also  used.  Allen  found  iron  oxid,  salt,  and  red  lead.  Starch- 
containing  materials  are  readily  detected  by  the  microscope 
or  by  the  iodin  test. 

Results  obtained  at  the  Connecticut  Agricultural  Experiment 
Station  indicate  that  pure  cayenne  pepper  will  contain  not  less 
than  16  per  cent,  of  non-volatile  ether-extract  and  between  4.5 
and  8  per  cent,  of  ash. 
27 


3o6  FOOD   ANALYSIS 

The  determinations  of  extract,  ash,  nitrogen,  and  moisture 
are  made  by  the  methods  elsewhere  given.  Barium  com- 
pounds have  been  found  in  some  samples,  and  it  has  been  al- 
leged that  they  are  normal,  but  this  seems  to  be  a  mistake. 

An  artificial  red,  containing  barium,  is  sometimes  used  to 
color  inferior  samples,  and  possibly  barium  sulfate  has  been 
added  as  a  make-weight. 
U.  S.  Standard. 

Non-volatile  ether 

extract not  less  than   - .  1 5.0   per  cent. 

Ash not  over    ..   6.5      "        '* 

Ash   insol.    in    hydro- 
chloric acid "        "     ..  0.5       "        '' 

Crude  fiber ''        ''     ..28.0      '' 

Starch ''        "     ..   1.5      "        '' 


GINGER 

Ginger  is  the  rhizome  of  the  Zingiber  zingiber  (L)  Karst.  It 
exists  in  commerce  in  two  forms,  with  the  outer  integument 
present,  called  "coated  ginger,"  and  removed  by  scraping,  as  in 
"uncoated"  or  "scraped  ginger."  Scraped  ginger  is  some- 
times known  as  white  ginger,  and  the  same  name  is  applied 
to  samples  that  have  been  bleached  either  with  sulfurous  acid 
or  hyposulfites.  It  is  also  sometimes  coated  with  lime  or  gyp- 
sum. Jamaica  ginger  is  preferred  in  the  United  States.  It 
forms  a  lighter  colored  powder  than  the  other  varieties.  Gin- 
ger contains  a  volatile  oil,  a  pungent  resin,  starch,  gum,  and  the 
usual  plant  constituents.  The  volatile  oil  has  the  odor  but 
not  the  pungency  of  ginger. 

Adulteration. — The  most  common  adulteration  of  ginger  is 
admixture  with  ginger  that  has  been  exhausted  with  dilute 
alcohol  or  water.  For  the  detection  of  this,  indications  are 
furnished  by  the  determination  of  the  cold-water  extract  taken 


GINGER  307 

in  conjunction  with  the  soluble  ash,  as  suggested  by  Allen  & 
Moor.     The  following  are  some  results  obtained : 

Jamaica. 

a.  b.  Cochin.  African. 

Moisture, i3-9        12.7  13.5  15.9 

Total  ash, 3.9  3.2  3.8  3.6 

Soluble  ash, 3.0  1.7  2.0  .  2.2 

Cold-water  extract, 14.4        12.2  8.6  10.8 

Neither  the  soluble  ash  nor  the  cold-water  extract  alone 
will  afford  a  means  of  deciding  as  to  the  presence  of  exhausted 
ginger,  but  by  a  combination  of  the  two  data  it  is  possible 
to  arrive  at  a  positive  conclusion.  Thus,  there  is  no  diffi- 
culty in  ascertaining  the  presence  of  the  adulterant  when  it 
has  been  added  in  such  quantities  as  to  bring  the  soluble  ash 
down  to  about  i  per  cent,  and  the  cold-water  extract  to  less 
than  8  per  cent.  Stock  recommends  also  a  determination  of 
the  amount  of  potassium.  The  following  are  some  results 
obtained  by  him : 

Soluble  Ash.         Potassium. 
Pure  ground  ginger  (94  samples), 1.7  to  3.6  0.7      to  1.5 

Exhausted  ginger, 0.2  to  1.6          0.016  to  0.7 

Turmeric,  flour,  ground  husks  and  shells,  seeds,  or  seed- 
cake are  possible  adulterants  of  ginger,  and  are  best  detected 
by  means  of  the  microscope.     The  form  of  the  starch  granules 
present  will  often  furnish  valuable  indications. 
U.  S.  Standard. 

Starch not  less  than   ..42.0    per  cent. 

Crude  fiber ''    more      ''     ..8.0      "        '' 

Calcium  oxid....  "       ''        "     ..   i.o      ''       " 

Ash "       "        "     ..  8.0      "       " 

Ash  insol.  in   hy- 
drochloric acid.''        "        ''     ..  3.0      "        " 

NUTMEG 

Nutmeg  is  the  kernel  of  the  seed  of  the  Myristica  jragrans 
Houttyn.     The  fruit  is  gathered  and  dried  by  slow  heating, 


3o8  FOOD   ANALYSIS 

after  which  the  shell  is  removed  and  the  inclosed  nutmeg  usually 
is  coated  by  dipping  in  thick  milk  of  lime.  The  nutmeg  is 
oval  or  elliptical  and  about  an  inch  in  length.  It  has  a  strong, 
pleasant  odor  and  v^arm,  aromatic  somewhat  bitter  taste.  Nut- 
megs contain  between  3  and  5  per  cent,  of  volatile  oil,  con- 
siderable fat,,  starch,  and  proteids.  The  volatile  oil  is  colorless 
or  pale  yellow  and  of  specific  gravity  0.92  to  0.95.  It  is  freely 
soluble  in  alcohol  and  commences  to  boil  at  160°.  It  is  dex- 
trorotatory. According  to  Cloez,  the  most  volatile  portion  is 
a  terpene  and  is  levorotatory.  There  is  present  also  myristicol, 
dextrorotatory  and  boiling  at  224°.  On  standing,  myristic  acid 
sometimes  separates  from  the  volatile  oil. 
U.  S.  Standard. 

Ash not  over    ..   5.0   per  cent. 

Ash    insol.    in    hydro- 
chloric acid ''        "     ..  0.5      ''        " 

Crude  fiber ''       "     ..lo.o      '' 

Non-volatile     ether-ex- 
tract  not  less  than  25.0      "        " 

Adulteration. — Nutmeg  is  little  subject  to  adulteration,  be- 
ing almost  exclusively  sold  unground.  Artificial  nutmegs, 
containing  some  nutmeg  oil,  are  said  to  have  been  prepared 
from  starchy  or  mineral  matter,  but  such  imitation  would  readily 
be  detected  by  the  appearance  of  the  cross-section  compared 
with  that  of  a  genuine  sample. 

For  methods  of  analysis,  see  under  "Cloves." 


MACE 

Mace  is  the  dried  mantle  or  arillus  of  the  nutmeg.  It  con- 
sists of  smooth  branching  bands  about  40  mm.  long,  2  mm. 
at  the  base,  and  thinner  above.  It  is  brownish,  has  an  odor 
like  nutmeg,  and  a  warm  aromatic  taste.     Mace  contains  a 


MACE  309 

volatile  oil  and  a  resin.  It  is  stated  that  it  contains  no  fat, 
but  this  does  not  accord  with  Spath's  statement,  given  below. 
According  to  FlUckiger,  there  is  also  present  an  uncrystallizable 
sugar  and  a  body  that  turns  blue  with  iodin,  and,  after  drying, 
reddish-violet.  It  appears  to  be  intermediate  between  starch 
and  mucilage. 
U.  S.  Standard. 

Ash not  over   3.0  per  cent. 

Ash  insol.  in  hydrochloric 

acid ''      "       0.5     " 

Crude  fiber ''      ''     lo.o     '' 

Non- volatile  ether  extract  .  20-30  "       " 

Adulteration. — In  addition  to  the  usual  spice  adukerants, 
mace  is  liable  to  contain  Bombay  mace,  a  variety  which  con- 
tains neither  the  fragrance  nor  the  taste  of  true  mace.  Starch- 
containing  adulterants  may  be  detected  by  the  fact  that  pure 
mace,  boiled  with  water,  yields  an  easily  fihered  solution,  which 
is  not  blued  by  iodin.  Determination  of  the  amount  of  starch 
will  furnish  a  rough  indication  of  the  proportion  of  adulterant 
present.  False  or  Bombay  mace  may  be  distinguished  by 
the  altered  proportion  of  volatile  oil  and  of  ether-extract.  The 
following  are  some  results  obtained  from  true  or  Java  mace 
compared  with  a  sample  of  false  mace : 

Fixed 
Lther- 
Water.         Ash.       Vol.  Oil.       extract.       Fiber.      Nitrogen. 

True  mace, 5.67  4.10  4.04  27.50  8.93           0.73 

"     4.86  2.65  8.66  29.08  4.48           0.98 

"    10.47  2.20  8.68  23.33  6.88          0.81 

"         "    18.21  1.62  3.37  21.90  3.70 

Bombay  mace, . .   7.04  1.36  0.27  56.75  8.17 

E.  Spath  extracted  a  number  of  samples  of  mace  with  petro- 
leum spirit  and  determined  the  constants  of  the  material  ob- 
tained. The  figures  obtained  from  mace  from  Banda,  Menado, 
Penang,  Macassar,  and  Zanzibar  closely  agreed  with  each  other : 


3IO  FOOD    ANALYSIS 

Melting-  Zeiss  Meissl 

POINT  Saponi-  Refracto-       Index  Number 

IN  Open  fication  Iodin           meter              of  (Banda 

Tube.  Number.  Number.        at  40^^.      Refraction.  Macc)- 

True  mace, 25-26       169.9-173      75.6-80.8     76-85     1.480-1.487       4.1-4.2 

Bombay  mace, -3 1-3 1. 5    189.4-191.4  50.4-53.5     48-49     1.463-1.464       i.o-i.i 

From   mace 

scales,      i.  e., 

"the  covering 

inside    the 

seed-mantle,"28.5-29    148. 2-148. 8     71.3-73.4 

According  to  Konig,  a  sample  containing  less  than  3  per  cent. 
of  volatile  oil  or  more  than  35  per  cent,  of  extract  on  the  dry  sub- 
stance cannot  be  regarded  as  true  mace.  False  mace  is  also 
distinguished  by  the  presence  of  a  peculiar  coloring-matter, 
analogous  to  that  of  turmeric,  rather  freely  soluble  in  alcohol 
and  but  slightly  soluble  in  ether.  The  large  oil  cells  of  the 
false  mace  contain,  according  to  Hanausek,  a  resinous  body 
with  which  alcohol  produces  a  yellow  or  greenish-yellow  solu- 
tion, turned  orange-red  by  alkalies.  If  10  to  20  c.c.  of  alcohol 
are  shaken  with  2  or  3  grams  of  powdered  mace  for  a  few  min- 
utes and  the  liquid  filtered,  the  filtrate,  but  not  the  filter-paper, 
becomes  colored.  In  the  case  of  false  mace  the  strongly  colored 
filtrate  dyes  the  paper  a  fixed  yellow.  If  the  filter  is  dried, 
freed  from  the  attached  powder,  and  touched  with  a  weak  al- 
kaline solution,  the  presence  of  turmeric  is  indicated  by  a  brown, 
and  of  false  mace  by  a  blood-red,  color.  If  the  alkali  be  re- 
moved by  washing  the  filter  with  w^ater,  a  trace  of  acid  will  be 
sufficient  to  bring  back  the  yellow.  Hafelman  suggests  de- 
composing an  alcoholic  extract  wdth  lead  acetate.  Genuine 
mace  gives  a  milk-white  turbidity;  false  mace,  even  when 
mixed  with  a  large  proportion  of  true  mace,  gives  a  red  floccu- 
lent  precipitate.  Turmeric  produces  a  somewhat  similar  color. 
If  a  strip  of  filter-paper  be  dipped  into  the  alcoholic  extract, 
gently  dried,  and  then  drawn  through  a  cold  saturated  solu- 
tion of  boric  acid  in  water,  the  presence  of  a  very  small 
quantity  of  turmeric  will  be  indicated  by  an  orange  or  red- 


ALLSPICE  311 

brown  tin.  With  false  mace,  on  the  other  hand,  the  yellow 
color  of  the  paper  will  remain  unchanged. 

Soltsien  has  called  attention  to  the  difference  between 
Bombay  and  Banda  mace  as  regards  the  quantity  of  matter 
extracted  by  ether  after  removal  of  the  fat-like  bodies  by 
petroleum  spirit,  and  suggests  that  advantage  be  taken  of  the 
fact  in  order  to  distinguish  between  the  two.  The  difference 
is  very  considerable,  the  quantity  being  about  ten  times  as 
great  with  Bombay  mace  as  with  true  mace.  Soltsien  has 
never  found  more  than  4.8  per  cent,  of  matter  extracted  by 
ether  in  a  pure  Banda  mace,  and  suggested  5.5  per  cent,  as  a 
maximum. 

The  examination  is  carried  out  as  follows:  10  grams  of 
powdered  mace  are  exhausted  with  boiling  petroleum  spirit 
in  a  flask  provided  with  a  well-cooled  inverted  condenser.  On 
cooling,  an  oily  portion  may  separate;  this  belongs  prop- 
erly to  the  extractive  matter  soluble  in  ether.  The  petroleum 
spirit  is  poured  off,  the  separated  oily  portion  in  the  flask 
washed  with  petroleum  spirit,  dissolved  in  absolute  ether, 
and  then  a  second  extraction  is  made  with  boiling  ether.  In 
the  ether-extract  there  is  also  a  tendency  of  a  portion  to  sep- 
arate out.  The  extract  is  poured  off,  the  separated  matter 
washed  with  ether,  and  the  washing  added  to  the  extract,  which 
is  then  fihered,  evaporated,  and  dried  in  the  water-bath,  the 
residue  being  weighed. 

ALLSPICE 

Allspice  or  pimento  is  the  dried  fruit  of  Pimenta  pimenta 
(L)  Karst.  It  is  nearly  globular,  6  mm.  or  less  in  diameter. 
Allspice  contains  volatile  oil,  fixed  oil,  resin,  tannin,  starch, 
sugar,  and  mucilage.  The  volatile  oil  is  similar  in  composition 
and  general  properties  to  oil  of  cloves.  The  yield  is  usually 
between  3  and  4  per  cent. 

Adulteration. — On  account  of  its  cheapness,  allspice  is  less 


312  FOOD   ANALYSIS 

subject  to  adulteration  than  other  spices.  In  addition  to  the 
usual  spice  admixtures,  clove  stems  and  the  lowest  grades  of 
cloves  are  sometimes  added.  These  latter  may  be  detected 
by  the  microscope,  and  also,  in  some  cases,  by  the  greatly  in- 
creased proportion  of  volatile  oil. 
U.  S.  Standard. 
Quercitannic  acid  (tannin),  not  less  than  8.0  per  cent. 

Total  ash,  not  more  than 6.0     "      " 

Ash  insol.  in  hydrochloric  acid,  not  over  0.5     ''      " 

Crude  fiber,  not  over 25.0     ''      '' 

A  sample  of  pure,  whole  Jamaica  allspice  examined  by 
Winton  gave  the  following  results: 

Volatile  oil,  3.52;  non-volatile  ether-extract,  6.48;  ash,  4.57 

1 2  samples  of  commercial  ground  allspice,  in  which  no  adul- 
terant could  be  detected,  gave  results  as  follows: 

Volatile  oil, 2 .05  to  2 .84 

Non-volatile  ether-extract, 3.98  to  5.62 

Ash, 4.62  to  5.50 

Analytic  Methods. — Moisture,  volatile  oil,  tannin,  and  fixed 
ether-extract  are  determined  as  described  on  pages  291  to 
293- 

CINNAMON 

Cinnamon  is  the  inner  bark  of  several  species  of  Cinnamo- 
mum.  Commercial  cinnamon  may  be  divided  into  three  classes 
as  follows: 

1.  True  or  Ceylon  cinnamon.  This  is  the  finest  quality, 
and  is  the  one  which  is  official  in  most  pharmacopeias.  It  is 
rarely  found  in  the  grocery  trade,  and  is  used  as  a. drug.  In 
its  preparation  for  the  market  it  is  deprived  entirely  of  the  outer 
coating  and  inner  cortical  layers,  and  forms  long  strips,  usually 
not  above  the  thickness  of  stout  writing-paper. 

2.  Common   or    Chinese    cinnamon,    known    as   cinnamon 


CINNAMON 


313 


cassia  or  cassia  bark.  It  is  thicker  than  true  cinnamon  and 
generally  covered  with  patches  of  cork.  It  has  a  less  delicate 
and  more  astringent  taste  than  true  cinnamon.  The  variety 
of  cassia  known  as  Saigon  cassia  is  said  to  have  greater  strength 
than  true  cinnamon. 

3.  Malabar  cinnamon,  including  inferior  quahties  from  the 
East  Indies  and  adjacent  mainlands,  from  which  the  common 
ground  cinnamon  of  the  retail  trade  is  usually  prepared. 

Microscopically,  true  cinnamon  may  be  distinguished  from 
cassia  by  the  presence  in  the  former  of  long  cells  of  woody  fiber, 
which  are  especially  well  shown  under  polarized  light. 

The  following  are  some  analyses  of  pure  samples : 


Analyst. 

Water 

Ethe- 
real 
Oil. 

Fixed 
Ether 

Ex- 
tract. 

Crude 
Fiber. 

Nitro- 
gen. 

Ash. 

Konig  and  Krauch 

Ceylon  cinna- 
mon,  .    .    . 

12.44 

1-45 

3546 

0.64 

3.28 

C.  Richardson 

Ceylon  cinna- 
mon,  .    .    . 

10.00 

3.14 

330 

16.18 

0.61 

370 

« 

Ceylon  cinna- 
mon, .    .    . 

5.40 

1.05 

1.66 

3308 

0.48 

4-55 

" 

Ceylon  cinna- 
mon,  .    .    . 

7-93 

0.82 

1.58 

25-63 

0.62 

340 

Kdnig  and  Krauch 

Cassia  bark,  . 

1395 

3-26 

17-72 

0.62 

2.22 

ti                  (( 

«        <( 

14.44 

•    • 

1.24 

17.76 

0.46 

1.96 

C.  Richardson 

((        << 

9.42 

58 

1.40 

17-73 

0.45 

2.3s 

(< 

((        << 

11.04 

1. 21 

1.86 

'5-45 

0.72 

2.48 

it 

* 

17-45 

0.55 

0.74 

14.33 

0.64 

5-25 

The  ash  of  pure  cinnamon  is  usually  white,  while  that  of 
cassia  is  often  brown,  due  to  the  larger  proportion  of  man- 
ganese oxid. 

The  items  volatile  oil,  alcohol-extract,  insoluble  ash,  and 
28 


314  FOOD   ANALYSIS 

nitrogen  appear  to  furnish  the  most  assistance  in  determining 
the  proportion  of  admixture. 

The  chemical  composition  of  cinnamon  and  cassia  is  in  the 
main  the  same.  Each  contains  a  volatile  oil,  tannin,  sugar, 
mannite,  starch,  and  mucilage.  The  essential  oil  of  Ceylon 
cinnamon  is  pale  yellow  or  reddish,  becoming  darker  and 
thicker  on  exposure,  and  depositing  crystals  of  cinnamic  acid. 
It  has  a  strong  odor  of  cinnamon  and  a  sweet,  warm,  aromatic 
taste.  The  specific  gravity  of  the  fresh  oil  is  1.035.  ^^  some 
cases  it  is  shghtly  levorotatory.  The  essential  oil  of  cassia 
has  similar  properties,  but  its  color  is  more  brownish,  taste 
less  sweet,  odor  less  delicate,  specific  gravity  greater  (1.055  to 
1.065),  and  is  sometimes  slightly  dextrorotatory.  Both  oils 
contain  variable  quantities  of  hydrocarbons,  but  consist  chiefly 
of  cinnamic  aldehyde,  and,  when  old,  contain  resin  and  cinna- 
mic acid. 

Adulteration. — The  chief  adulteration  consists  in  the  substi- 
tution of  the  inferior  cassia  for  the  true  cinnamon.  As  noted 
above,  the  true  cinnamon  is  now  only  obtained  as  a  drug.  They 
may  be  distinguished  by  the  difference  in  their  microscopic 
characters.  Aside  from  this,  the  most  important  adulteration 
consists  in  the  partial  abstraction  of  the  ethereal  oil,  on  which 
the  value  of  the  spice  depends,  either  by  alcohol  or  by  distilla- 
tion with  water.  Sophistication  of  this  kind  is  difficult  to  de- 
tect, by  reason  of  the  variations  of  the  original  bark  in  com- 
position. The  lower  grades  of  ground  cinnamon  are  also  adul- 
terated with  barks  of  allied  species,  refuse  found  in  the  bundles 
of  cinnamon  as  imported,  mahogany  and  other  woods,  flours 
of  various  kinds,  oil-cake,  and  similar  materials.  These  are 
often  readily  detected  by  the  microscope. 

U.  S.  Standard  for  ground  cinnamon  or  ground  cassia. 

Ash,  not  over 8.0  per  cent. 

Sand,"      ''    2.0    "      '' 


CLOVES  315 

In  Austria,  Bavaria,  and  Switzeriand,  cinnamon  or  cassia 
containing  more  than  5  per  cent,  of  ash  or  i  per  cent,  of  sand 
is  held  to  be  adulterated. 


CLOVES 

Cloves  are  the  unexpanded  flowers  of  the  Eugenia  aromatica 
O.  Kuntze.  They  consist  of  a  dark  brown,  cylindrical  calyx, 
3  to  4  mm.  thick,  bearing  a  several-celled  ovary  and  a  globular 
head  of  four  petals.      Many  oil  glands  are  under  the  epidermis. 

Cloves  contain  a  volatile  oil,  resin,  tannin,  and  gum,  but  no 
starch.  The  volatile  oil  is  thicker  than  most  essential  oils  and 
becomes  still  thicker  and  darker  with  age.  It  has  the  odor  of 
cloves  and  a  burning  aromatic  taste.  Its  specific  gravity  is 
from  1034  to  1056;  it  boils  at  240°.  The  oil  obtained  from 
clove  stalks  has  a  specific  gravity  of  1.009.  Oil  of  cloves  dis- 
solves freely  in  alcohol.  Strong  solution  of  potassium  hydroxid 
converts  it  into  a  crystalline  mass  of  potassium  eugenate.  It 
is  sometimes  slightly  dextrorotatory.  It  consists  principally  of 
a  hydrocarbon  and  eugenol  (eugenic  acid).  On  distilling  a 
mixture  of  cloves  and  potassium  hydroxid  solution,  the  hydro- 
carbon is  obtained  as  an  oil  of  specific  gravity  0.918,  boiling  at 
251°.  By  decomposing  potassium  eugenate  with  sulfuric  acid 
and  distilling,  eugenic  acid  is  obtained  as  a  colorless  oil  of  spe- 
cific gravity  from  1076  to  1078,  boiling  at  247.5°.  Caryophyl- 
lin  and  a  salicylic  ester  have  also  been  found. 

Adulterations. — In  addition  to  the  adulterants  usually  em- 
ployed for  ground  spices,  clove  stems  and  the  fruit  of  the  clove, 
the  so-called  ''mother-cloves,"  may  be  added.  Clove  stems 
may  be  detected  by  the  microscope  by  the  presence  of  numerous 
stone  cells,  bast  fibers,  and  scaliform  ducts.  The  form  of  the 
stone  cells  varies  greatly;  the  walls  are  thick  and  the  interior 
cavity  may  be  simple  or  ramifying.  The  bast  fibers  are  usually 
long,  spindle-shaped,  and  thick.     The  scaliform  ducts,  together 


3i6 


FOOD   ANALYSIS 


with  the  stone  cells,  are  the  best  evidence  of  the  presence  of 
clove  stems.  In  mother- cloves,  the  stone  cells  are  very  thick- 
walled  and  have  a  nodulated  exterior,  which  enables  them  to 
be  distinguished  easily.  The  seeds  contain  starch  and  raph- 
ides.  The  starch  granules  resemble  those  of  some  kinds  of 
arrowroot;  they  are  principally  pear-shaped,  or,  rather,  slender 
and  slightly  curved,  generally  single,  and  show  a  well-marked 
cross  under  polarized  light.  There  is  a  small  hilum  at  the 
broad  end.  The  resemblance  to  arrowroot  starch  is  not  likely 
to  cause  confusion,  as  the  latter  is  too  costly  for  use  as  an  adul- 
terant. 

Cloves  are  also  adulterated  by  the  addition  of  samples  from 
which  a  portion  of  the  essential  oil  has  been  removed.  This 
is  usually  difficult  of  detection  on  account  of  the  great  varia- 
tion in  the  amount  of  oil  found  in  pure  samples. 

ANALYSES  OF  CLOVES  AND  STEMS 


Water, 

Ash, 

Volatile  Oil,  .  .  . 
Fixed  ether-residue, 
Crude  fiber,  .  .  . 
Nitrogen,  .... 
Analyst, 


Whole  Cloves. 


16.39 

4.«4 
16.98 

6.20 
10.56 

0-95 
Laube  and 
Allendorf 


2.90  to  10.67 


5-25  " 
10.23  " 

7.12" 

6.18" 
0.76  " 

Richardson, 
7  samples 


1305 
18.89 
10.24 

9-75 
1. 12 


9  to  21 


Dietsch 


Stems. 


10.18 

6.96 

4.40 

403 
1358 

0.92 
Richardson 


In  20  samples,  either  known  to  be  pure  or  in  which  no  adul- 
teration could  be  detected  by  the  microscope,  Winton  found 
the  following  range  in  composition: 


Per  Cent. 

Volatile  oil, 10.01  to  18.32 

Fixed  ether-extract, 4.90  "    6.20 

Ash, 6.50  "    7.95 


MUSTARD  317 

U.  S.  Standard. 

Volatile  ether-extract,  not  less  than lo.o  per  cent. 

Quercitannic  acid  (tannin),  not  less  than.  .12.0     "     " 

Total  ash,  not  more  than 8.0     "       " 

Ash  insoluble  in  hydrochloric  acid,  not  more 

than 0.5     ''     '' 

Crude  fiber  not  more  than lo.o    "     " 

Analytic  Methods. — Moisture,  volatile  oil,  tannin  and 
ether-extract  are  determined  by  the  methods  given  on  pages 
291  to  293.  Crude  fiber  is  determined  on  the  residue  from  the 
ether-extract. 


MUSTARD 

Mustard  is  prepared  from  the  seeds  of  the  Brassica  nigra 
Koch  (black  mustard)  and  B.  alba  Hkr.  f.  (white  mustard). 
Commercial  mustard  may  be  a  mixture  of  the  two  forms.  The 
seeds  are  finely  powdered  and  passed  through  a  sieve  in  order 
to  remove  husks.  Both  forms  contain  a  fixed  oil  in  fairly  con- 
stant proportion,  albuminous  matter,  gum,  sinapin  thiocyanate, 
and  an  enzym,  myrosin,  but  no  starch.  White  mustard  con- 
tains also  the  glucosid,  sinalbin;  and  black  mustard  the  glu- 
cosid,  potassium  myronate.  These  glucosids  are  decomposed 
by  the  enzym,  on  addition  of  water. 

Allyl  isothiocyanatCy  volatile  oil  of  mustard,  is  a  colorless 
liquid,  specific  gravity  ^fo  1.018,  boiling  at  148°-! 50°,  and  vola- 
tile in  a  current  of  steam.  It  has  a  strong  mustard-like  odor  and 
the  vapor  excites  a  flow  of  tears.  It  is  slightly  soluble  in  water 
and  much  more  so  in  alcohol,  ether,  petroleum  spirit,  and  carbon 
disulfid.     It  is  a  powerful  rubefacient  and  vesicant. 

Acrinyl  isothiocyanate  is  a  yellow  liquid  of  pungent  burning 
taste.  It  is  a  less  powerful  vesicant  than  the  oil  from  black 
mustard  and  is  but  slightly  volatile  in  steam.  It  is  insoluble 
in  water,  but  soluble  in  alcohol  and  ether. 


31 8  FOOD  ANALYSIS 

Myrosin  is  coagulated  by  heat,  so  that  if  mustard  be  intro- 
duced into  boiling  water,  no  volatile  oil  is  produced. 

The  fixed  oil  of  mustard  has  the  following  physical  and 
chemical  constants:  Sp.  gr.,  ^,  0.914  to  0.920;  saponifica- 
tion value,  170  to  175;  iodin  value,  92  to  106.  About  35  per 
cent,  is  usually  present.  Commercial  samples  of  good  quality 
may  contain  much  less,  a  portion  having  been  expressed  in 
the  manufacture  of  the  mustard  flour. 

The  following  are  some  results  of  examination  of  pure  samples : 

Mean  of  three  closely  concordant  analyses  of  white  mustard 
by  Leeds  and  Everhart: 

Water, 6.83  per  cent. 

Potassium  myronate, 0.64 

Sinapin  thiocyanate, 11.12 

Myrosin  and  albumin, 28.48 

Fixed  oil, 29.21 

Ash, 3.75 

Variations  in  composition  of  ground  mustard  seeds,  accord- 
ing to  figures  published  by  A.  O.  A.  C. : 

Per  Cent. 

Moisture, 3  to    8 

Ash, 4  to    7 

Ether-extract, 31  to  37 

Fiber, 4  to    6.5 

Aqueous  extract, 30  to  38 

Sulfur, I  to    1.6 

When  prepared  from  partially  expressed  seeds,  the  mustard 
will  contain  less  oil  (ether-extract)  and  a  correspondingly  larger 
proportion  of  the  other  ingredients. 

Adulteration. — The  most  common  adulterant  for  mustard  is 
rice  flour  or  wheat  flour.  These  are  readily  detected  by  the 
microscope  and  by  the  presence  of  starch.  This  may  also  be 
present  as  a  constituent  of  turmeric,  added  to  color  pale  samples. 
Starch  may  be  detected  by  boihng  a  portion  of  the  sample  with 
water,  filtering,  and  adding  iodin  to  the  filtrate.  It  is  determined 
as  on  page  93.     The  proportion  of  starch  in  wheat  flour  is  about 


MUSTARD  319 

72  per  cent.  Allen  suggests  the  determination  of  the  amount 
of  fixed  oil,  which  is  usually  about  35  per  cent.,  and  calculat- 
ing from  its  deficiency  the  proportion  of  diluent  present.  In 
view  of  the  practice  of  some  manufacturers  of  pressing  the 
seed,  such  a  method  is  no  longer  reliable,  but  may  often  be  of 
value  as  corroborative  evidence. 

Of  mineral  additions,  calcium  sulfate,  chalk,  and  lead  chro- 
mate  have  been  employed.     These  are  detected  in  the  ash. 

Leach^^  has  made  special  investigations  into  the  characters 
of  commercial  mustards. 

Volatile  oil.  For  the  determination  of  this,  which,  as 
noted  above,  does  not  pre-exist  in  the  seed,  Leach  recommends 
Roeser's  method : 

5  grams  of  the  sample  are  mixed  with  60  c.c.  of  water 
and  15  c.c.  of  60  per  cent,  alcohol,  allowed  to  stand  for  two 
hours,  and  then  distilled  into  a  flask  containing  10  c.c.  of 
ammonium  hydroxid,  until  50  c.c.  of  the  original  liquid  has 
passed  over.  The  distillate  is  mixed  wdth  10  c.c.  of  —^- 
silver  nitrate,  allowed  to  stand  24  hours,  made  up  to  100  c.c, 
filtered,  50  c.c.  of  the  filtrate  mixed  with  5  c.c.  of  --  potas- 
sium cyanid  solution,  and  the  excess  of  cyanid  titrated  with 
-^  silver  nitrate,  using  a  5  per  cent,  solution  of  potassium 
iodid  as  indicator.  The  number  of  c.c.  of  ^^  silver  nitrate 
taken  up  by  the  oil,  multiplied  by  0.6274,  will  give  the  per- 
centage of  volatile  oil  of  mustard. 

Although  mustard  contains  no  starch.  Leach  points  out 
that  some  of  the  tissue  of  the  seed  will  produce  a  reducing 
sugar  even  by  the  diastase  method,  so  that  error  may  be  made 
in  this  respect.  It  must  also  be  borne  in  mind  that  mustard 
may  be  gathered  from  fields  in  which  starch-bearing  weeds 
are  growing,  and  thus  admixture  with  starch  occur.  Leach 
found  starch  grains  due  to  this  cause  abundantly  in  a  Dakota 
mustard-flour.     Such   admixture   can   be   easily   detected   by 


320  FOOD   ANALYSIS 

the    microscope,    using    the    potassium    iodid-iodin    solution, 
page  26.     Pure  mustard  flour  will  not  give  blue  granules. 
U.  S.  Standard. 
Starch  (calculated  from  the  reducing  sugar 

obtained  by  diastase  method),  not  over  2.5  per  cent. 

Total  ash,  not  over 8.0     ''     " 

Coloring-matters  are  frequently  added,  the  most  common 
being  turmeric,  Martius'  yellow,  and  naphthol  yellow  S.  Coal- 
tar  colors  may  be  detected  by  methods  given  on  pages  64- 
75;  turmeric,  by  the  test  given  under  ''Mace"  or  by  the 
principle  of  the  test  for  boric  acid,  page  82. 

FLAVORING  EXTRACTS 

Vanilla  Extract. — Vanilla  is  the  pod  of  Vanilla  planijolia, 
an  epiphytic  orchid  of  tropical  regions.  Its  flavor  depends  on 
an  aldehydic  benzene  derivative  called  vanillin.  The  amount 
present  differs  much  in  different  samples  and  bears  no  constant 
relation  to  the  source  or  price  of  the  pod. 

The  most  expensive  grades  of  extract  are  made  by  macera- 
ting vanilla  beans  in  50  per  cent,  alcohol.  The  cheaper  grades 
contain  cumarin  (from  Tonka  bean),  artificial  vanillin,  some 
glycerol,  and  caramel  or  coal-tar  colors.  The  cumarin  may  be 
either  added  as  such  or  obtained  by  macerating  tonka  beans 
in  the  solvent.  In  cheap  extracts  a  very  dilute  alcohol  is  used 
and  the  solvent  action  often  aided  by  some  alkaline  substance, 
generally  acid  potassium  carbonate.  The  following  is  a  pub- 
lished formula  for  a  very  cheap  imitation  extract: 

Vanillin, i  gram. 

Cumarin, i  gram. 

Alcohol, 1 25  c.'c. 

Glycerol, 65  c.c. 

Water, i  liter. 

Caramel  to  color. 

Commercial  vanilla  extracts  have  been  examined  by  Hess.^^ 


FLAVORING   EXTRACTS  32 1 

He  gives  the  following  test  as  a  critical  one:  A  portion  of  the 
sample  should  be  mixed  with  a  few  drops  of  lead  acetate  solu- 
tion; if  a  bulky  flocculent  precipitate  does  not  form,  the  extract 
is  not  of  high  quality.  The  process  given  by  Hess  may  then 
be  applied  to  establish  its  general  character: 

5  c.c.  of  the  extract  are  diluted  slowly  with  lo  c.c.  of  water 
and  the  mixture  shaken.  A  flocculent  reddish-brown  precipitate 
shows  that  no  alkali  has  been  added.  A  milky  solution  in- 
dicates a  foreign  resin.  Hydrochloric  acid  is  added  drop  by 
drop  to  a  portion  of  the  diluted  liquid;  only  a  slight  turbidity 
should  result.  If  the  turbidity  is  considerable  and  the  color 
fades,  alkali  has  been  employed  in  making  the  extract. 

25  c.c.  of  the  sample  are  concentrated  on  a  water-bath  until 
the  alcohol  is  removed  and  made  up  to  the  original  volume 
with  water.  The  vanilla  resin  will  appear  as  an  amorphous, 
flocculent,  reddish-brown  mass  if  alkali  be  present.  The  cold 
solution  is  acidified  with  hydrochloric  acid,  when  the  whole  of 
the  resin  will  separate,  leaving  the  liquid  nearly  colorless. 
Afjter  standing  several  hours  the  residue  should  be  collected  on 
a  filter,  washed  with  water,  and  the  filtrate  and  precipitate 
further  tested. 

A  piece  of  the  filter  with  resin  attached  is  placed  in  sodium 
hydroxid  solution.  A  deep  red  solution  should  be  formed: 
A  solution  of  the  portion  of  the  precipitate  in  alcohol  should 
not  give  any  marked  reaction  with  ferric  chlorid  or  hydrochloric 
acid. 

A  portion  of  the  filtrate  is  concentrated  at  a  low  temperature 
until  its  color  approximates  that  of  the  original  sample,  a  few 
drops  of  strong  hydrochloric  acid  are  added,  and  gently  heated. 
Caramel  will  produce  a  yellowish-red  flocculent  precipitate. 
The  liquid  is  allowed  to  cool,  filtered,  and  the  precipitate  washed 
with  water;  if  from  caramel,  the  precipitate  will  be  insoluble  in 
water,  alcohol,  and  ether,  soluble  in  sodium  hydroxid,  glacial 
acetic  acid,  and  dilute  alcohol. 


322  FOOD   ANALYSIS 

A  small  portion  of  the  filtrate  is  made  alkaline  with  am- 
monium hydroxid;  natural  color  is  much  deepened.  Zinc 
di^st  is  added,  and  the  liquid  warmed  gently.  The  color  should 
return  to  about  the  tint  it  possessed  before  the  ammonium  hy- 
droxid was  added,  but  azo-colors  will  be  completely  bleached. 
If  the  latter  effect  occurs,  some  of  the  liquid  should  be  mixed 
with  hydrogen  dioxid,  when  the  color  will  return. 

The  caramel  test  described  on  page  124  will  probably  be  of 
service  in  these  examinations. 

Determination  of  Vanillin. — A  rapid  valuation  of  vanilla  ex- 
tracts may  be  made  by  the  following  colorimetric  method. ^^ 
Several  reagents  are  required. 

Lead  hydroxid. — 200  grams  of  lead  acetate  are  dissolved  in 
about  800  c.c.  of  water,  the  liquid  filtered,  a  solution  of  potas- 
sium hydroxid  added  in  slight  excess,  and  the  precipitate  washed 
several  times  until  free  from  alkali.  It  should  be  kept  mixed 
with  excess  of  water  in  a  well- stoppered  bottle,  the  mixture  be- 
ing shaken  when  used. 

Bromin  water. — Saturated  solution  of  bromin  in  water. 

Ferrous  sulfate. — Freshly-prepared,  10  per  cent,  solution  in 
water. 

Standard  Vanillin. — Freshly-prepared  solution  0.050  gram 
vanillin  in  25  c.c.  of  alcohol,  made  up  to  100  c.c.  with  water. 
I  c.c.  contains  0.0005  vanillin. 

2  c.c.  of  the  vanilla  extract  are  mixed  in  a  test-tube  with 
sufficient  lead  hydroxid  to  decolorize,  the  mixture  transferred 
to  a  filter,  washed  and  the  filtrate  and  washings  mixed.  A 
little  bromin-water  is  added  and  then  the  ferrous  sulfate  solu- 
tion until  the  bluish-green  does  not  increase.  The  color  thus 
obtained  is  compared  with  similar  volumes  of  liquid  containing 
known  amounts  of  vanillin  treated  in  the  same  way.  These 
comparison  solutions  are  made  by  diluting  with  water,  different 
measures  of  the  standard  vanillin  solution,  and  adding  the 
reagents.     Thus  i  c.c.  of  the  solution  contains  0.00005  vanillin. 


FLAVORING   EXTRACTS  323 

Dilute  solutions  may  be  made  with  quantities  of  the  standard 
ranging  from  0.5  c.c.  to  5  c.c,  but  after  a  little  practice  in  this 
class  of  testing,  it  becomes  easy  to  approximate  the  color,  and 
only  a  few  comparison  dilutions  need  be  made.  The  liquids 
compared  should  be  made  up  to  the  same  volume  and  examined 
in  colorless  tubes  of  sensibly  identical  size  and  shape.  The  so- 
called  ''  Nessler  tubes  "  for  water  analysis  are  preferable.  These 
are  marked  at  50  c.c,  a  convenient  volume. 

For  the  exact  determination  of  vanillin  (and  cumarin)  the 
following  process  is  recommended.  It  is  Hess  &  Prescott's  ^* 
method  modified  by  Winton^^: 

25  grams  of  extract  are  evaporated  on  the  water-bath  at  a 
temperature  not  exceeding  80° — with  occasional  addition  of  water 
to  maintain  the  volume — until  all  alcohol  is  removed.  Lead 
acetate  solution  is  added  drop  by  drop  until  no  further  pre- 
cipitate forms,  the  liquid  is  stirred  to  promote  flocculation, 
filtered  through  a  wet  filter,  and  the  precipitate  washed  three 
times  with  hot  water.  The  mixed  filtrates  are  allowed  to  cool, 
and  extracted  four  times  with  ether,  using  about  15  c.c.  each 
time.  The  completion  of  the  extraction  may  be  determined 
by  evaporating  a  few  drops  of  the  ether  on  a  watch  glass;  no 
appreciable  residue  should  be  left.  The  combined  ether  ex- 
tracts, which  contain  all  of  the  vanillin  and  cumarin,  are  shaken 
five  times  with  2  per  cent,  solution  of  ammonium  hydroxid,  using 
10  c.c.  for  the  first  time  and  5  c.c.  for  the  subsequent  ones.  The 
whole  of  the  vanillin  will  pass  into  the  ammonium  hydroxid. 

The  ether  is  washed  into  a  weighed  dish  and  allowed  to  evap- 
orate at  room  temperature,  then  dried  in  a  desiccator  and  the 
weight  of  residue  (cumarin)  taken. 

The  vanillin  solution  is  rendered  slightly  acid  by  hydro- 
chloric acid,  shaken  with  four  portions  of  ether  as  at  first,  the 
portions  mixed,  evaporated  at  room  temperature,  dried  over 
sulfuric  acid  and  weighed. 

The  vanillin  and  cumarin  thus  obtained  may  not  be  pure. 


324  FOOD   ANALYSIS 

and  if  very  accurate  determination  is  needed,  each  residue 
should  be  separately  dissolved  in  petroleum  spirit,  boiling  at 
about  35°  (commonly  sold  as  "legroin"),  using  small  portions 
at  a  time  until  all  the  soluble  material  is  dissolved.  The  un- 
dissolved matter  is  dried  for  a  few  minutes  at  100°,  weighed 
and  deducted  from  the  first  weight.  The  ligroin  solution  of 
vanillin  evaporated  at  room  temperature  and  dried  in  a  desic- 
cator should  leave  a  residue  melting  at  8o°-8i°  and  having  the 
odor  of  vaniUin.     Synthetic  and  natural  vanillin  are  identical. 

The  cumarin  solution  evaporated  at  room  temperature  should 
leave  a  residue  melting  at  67°  and  having  the  odor  of  cumarin. 

Leach^^  states  that  vanillin  and  cumarin,  crystallized  from 
ether,  show  differences  with  crossed  rjcols,  vanillin  giving,  even 
without  selenite,  marked  color,  but  cumarin  none.  Vanillin 
gives  a  more  marked  color  with  sodium  nitrite  and  sulfanilic 
acid,   but   the   reaction   is    not   characteristic. 

Lemon  extract  is  a  solution  of  lemon  oil  and  the  soluble 
matters  of  lemon  peel  in  alcohol.  The  lemon  peel  is  principally 
for  coloring  purposes.  Commercial  lemon  extracts  depart 
much  from  this  standard.  The  lemon  oil  is  often  in  small 
amount,  even  absent;  other  oils  are  substituted  and  coloring 
matters  other  than  lemon  peel.  Methyl  alcohol  may  be  present. 
The  Pharmacopeia  standard  is  5.0  per  cent,  of  lemon  oil,  but 
it  must  be  borne  in  mind  that  this  is  a  drug-  not  a  food- 
standard.  Some  commercial  extracts  will  exceed  this.  The 
following  formula  for  a  cheap  lemon-extract  is  quoted  from  a 
trade  circular: 

Lemon  oil, i     gram 

Lemon-grass  oil, o  i  c.c. 

Citric  acid, 0.5  c.c. 

Alcohol, 16.0  c.c. 

Water, i  lo.o  c.c. 

Turmeric  tincture  to  color. 

Lemon  Oil. — This  is  principally  the  dextrorotatory  form  of 


FLAVORING   EXTRACTS  325 

a  terpene  hydrocarbon,  limonene,  with  an  aldehyde,  citral, 
and  smaller  amounts  of  analogous  bodies.  Lemon  oil  is  in- 
soluble in  weak  alcohol. 

Oil  oj  citronella  and  oil  oj  lemon-grass  are  volatile  oils  of  the 
same  general  character  as  lemon  oil  and  often  substituted 
for  it. 

The  examination  of  lemon  extract  is  directed  principally  to 
the  determination  of  the  amount  of  lemon  oil,  and  the  detec- 
tion of  added  colors  and  methyl  alcohol.  The  methods  have 
been  carefully  investigated  by  Mitchell,^^  and  his  results  are  here 
summarized. 

Lemon  oil  may  be  detected  by  diluting  the  extract  with 
considerable  water.  If  no  turbidity  results,  the  oil  is  not  present 
in  appreciable  amount.  In  the  absence  of  other  optically 
active  bodies  the  amount  may  be  determined  by  the  polarimeter, 
using  a  200  mm.  tube.  The  sugar-scale  reading  divided  by 
3.2  will  give  the  percentage  of  oil.  Sucrose  may,  however, 
be  present.  If  this  is  the  case,  lo  c.c.  of  the  sample  must  be 
evaporated  to  dryness,  washed  several  times  with  portions  of 
5  c.c.  of  ether,  the  residue  dried  and  weighed,  and  for  each 
0.1  of  this  0.38  is  deducted  from  the  calculated  percentage  of 
oil. 

Added  colors. — The  detection  of  these  will  be  along  the  lines 
indicated  on  pages  64  to  75.  The  addition  of  hydrochloric  acid 
may  give  useful  indications.  Turmeric,  naphthol  yellow  S,  nat- 
ural lemon  color  and  fustic  yellow  are  not  affected;  azo- colors 
are  turned  pink,  dinitrocresols  and  naphthol  yellow  (Mar- 
tius'  yellow)  are  bleached. 

Sucrose^  Invert  Sugar  and  Glycerol  will  be  indicated  in  the 
residue  on  evaporation.  Capsicum  will  be  detected  in  this  by 
taste.  Invert  sugar  is,  of  course,  also  indicated  by  the  levoro- 
tatory  reading. 

For  the  detection  of  citric  and  tartaric  acids  see  under  ''Fruit 
Sirups." 


326  FOOD   ANALYSIS 

A  special  test  for  citral,  citronellal  and  limonene  is  given  by 
Burgess  ^^:  10  grams  of  mercuric  sulfate  are  dissolved  in  a  mix- 
ture of  20  c.c.  sulfuric  acid  and  85  c.c.  of  water.  2  c.c.  of  the 
sample  are  shaken  in  a  closed  test-tube  with  5  c.c.  of  this  reagent. 
The  following  results  are  noted:  Citral,  bright  red  liquid 
quickly  changing  to  a  white  floating  material;  Citronellal, 
bright  yellow  not  quickly  fading;  Limonene,  transient  flesh 
tint  fading  to  white. 

The  oil  may  also  be  determined  directly.  20  c.c.  of  the  sam- 
ple are  introduced  into  a  milk-testing  bottle  (seepage  203),  i  c.c. 
of  diluted  hydrochloric  acid  (1:1)  added,  and  then  25  c.c.  water, 
previously  warmed  to  60°.  The  liquids  are  mixed  and  allowed 
to  stand  for  5  minutes  in  water  at  60°.  The  tube  is  whirled  in 
the  milk- centrifuge  for  5  minutes,  warm  water  added  until  the 
oil  is  brought  into  the  graduated  neck,  then  again  whirled  for 
a  few  minutes,  allowed  to  stand  in  water  at  60°  for  a  short 
time  and  the  volume  of  separated  oil  read  off.  If  the  volume 
is  over  2  per  cent.,  add  0.4  as  a  correction  for  oil  in  solution;  if 
between  i  and  2  per  cent.,  add  0.3  for  this  correction.  Of 
course,  these  tubes  must  be  operated  in  pairs.  The  oil  thus  ob- 
tained may  be  used  for  several  tests.  To  obtain  the  percentage 
in  the  original  extract,  multiply  the  observed  volume  by  0.86 
(specific  gravity  of  lemon  oil  at  15.5°)  and  divide  by  the  specific 
gravity  of  the  extract. 

Alcohol. — If  the  extract  contains  no  other  substances  than 
oil,  alcohol  and  extractives  of  the  lemon-peel,  the  specific  gravity 
may  be  taken  and  the  equivalent  proportion  of  alcohol  cal- 
culated from  the  usual  tables.  Deducting  from  this  the  per- 
centage of  lemon  oil,  the  remainder  will  be  alcohol.  If  an 
absolute  determination  of  alcohol  is  desired,  50  c.c.  of  the  sample 
should  be  diluted  to  200  c.c.  with  water,  the  mixture  shaken 
with  5  grams  of  magnesium  carbonate,  filtered  through  a  dry 
filter,  distilled,  and  the  percentage  of  alcohol  determined  by  the 
specific  gravity. 


FRUIT   JUICES,    SIRUPS,   JELLIES   AND   JAMS  327 

Methyl  alcohol  is  detected  by  the  test  given  in  connection  with 
the  examination  of  alcoholic  beverages.  The  absence  of  formal- 
dehyde should  be  ensured  before  making  this  test.  For  the 
method  of  detecting  it  see  page  ^;^  and  for  a  method  of  removing 
it  before  testing  for  methyl  alcohol,  see  under  "Alcoholic 
Beverages." 

The  tabulated  results  of  a  systematic  examination  of  lemon 
extract  sold  in  Massachusetts  in  1901,  reported  by  Leach,^®  show 
the  following  range  of  composition.  The  polarization  is  in 
200  mm.  tube  and  on  sugar  scale : 

Standard.  Adulterated. 

Polarization, 17 .0-30.8  0.0-14.0 

Lemon  oil, 5.0-9.1  0.0-4.1 

Specific  gravity  (15.6°), 0.8268-0.8296  0.8416-0.9937 

Alcohol  per  cent,  by  volume, 80.0-^86.8  4.49-87.5 

Two  of  the  samples  included  under  "standard"  contained 
added  color,  turmeric  in  one  and  dinitrocresol  in  the  other. 

One  adulterated  sample,  not  included  in  the  above  summary, 
gave  a  polarimetric  reading  of  — 8.0.  It  contained  invert  sugar. 
Another  sample,  also,  not  included  above,  gave  a  reading  of 
27.0.  It  contained  sucrose.  The  adulterated  samples  were 
mostly  colored,  azo-dyes  and  dinitrocresol  being  most  frequently 
used.  A  considerable  number  of  the  samples  contained  no 
lemon  oil. 


FRUIT  JUICES,    SIRUPS,   JELLIES   AND   JAMS 

Fruit  juices  are  made  by  pressing  the  fruit  and  straining  the 
liquid  portions.  Jellies  are  prepared  by  boiling  the  juice,  with 
or  without  addition  of  sucrose,  until  the  mass  sets  on  coohng. 
The  setting  is  due  principally  to  pectin,  a  non-nitrogenous 
body  bearing  some  analogy  to  the  carbohydrates.  Jams  are 
made  by  concentrating  the  juice  by  boiling,  without  straining, 
and  adding  considerable  sucrose. 


328  FOOD   ANALYSIS 

The  composition  of  these  products  is  shown  in  the  following 
table  from  the  analyses  of  Tolman,  Munson  and  Bigelow^^: 

Fruit  Juices. 

(Prepared  by  adding  a  convenient  amount  of  water,  cooking  until  the  fruit 

is  soft  and  straining  through  muslin.) 

Total  Reducing  Polar,  at  18° 

Solids.         Ash.  Sugar.     Sucrose.     Sugar  Scale. 

Apple  (pippin), 7.95  0.47  4.00  1.18  —3.0 

Crab-apple, 5.62  0.20  2.56  1.03  — i.o 

Grape  (cultivated), 8.83  0.57  5.10  0.89  - — 1.2 

Blackberr5^, 8.54  0.52  4.34  0.00  — 1.5 

Huckleberry, ^^-33  040  11. 21  0.89  — 3.2 

Peach, 8.90  0.45  —  4.59  4.0 

Pear  (Bartlett), 11.65  0.45  5.87  1.18  —4.8 

Plum  (Damson), 12.72  0.63  4.86  0.51  2.0 

Jellies. 
(Fruit  juices  concentrated,  strained  and  sucrose  added.) 

Total  Solids.      Ash.  Red.  Sugar.  Sucrose. 

Apple  (pippin), 59-i8            0.22  20.78  33-04 

Crab-apple, 63.28            o.ii  34-93  23.68 

Grape  (cultivated), 63.66           0.45  32.29  30-52 

Blackberry, 59.63            0.33  12.51  44.90 

Huckleberry, 63.02            0.28  32.29  30-52 

Peach, 69.98            0.21  8.75  56.59 

Pear  (Bartlett), 69.12            0.34  6.58  58.46 

Plum  (Damson), 45-5^            0.68  19.18  22.67 

Jams. 

(Moderate  concentration  and  addition  of  sucrose.) 

Total  Solids.  Ash.  Red.  Sugar.      Sucrose. 

Apple  (pippin), 63.22  0.20  25.52  29.11 

Crab-apple, 41.82  0.27  14.80  23.04 

Grape  (cultivated), 56.64  0.48  33.44  11.33 

Blackberry, 55-42  0.48  18.77  29.00 

,,            Pear  (Bartlett), 61.52  0.28  13-20  33-74 

Plum  (Damson), 50.43  0.54  28.29  9.70 

The  proteids  in  the  juices  are  much  below  i  per  cent.;  the 
acidity  expressed  as  sulfuric  acid  is  also  below  i  per  cent.,  but 
in  the  grape  is  slightly  over  0.9.  The  sucrose  added  to  the  jellies 
and  jams  has  been  largely  inverted  by  the  fruit- acids,  hence 
the  reducing  sugar  is  greatly  increased. 


FRUIT  JUICES,   SIRUPS,   JELLIES  AND  JAMS  329 

Ripe  cranberries  contain  notable  amounts  of  benzoic  acid. 
G.  F.  Mason,®^  who  has  recently  made  a  careful  study  of  this, 
found  about  i  part  of  benzoic  acid  to  2000  parts  of  the  fresh 
pulp,  a  quantity  sufficient  to  act  as  a  preservative.  The  occur- 
rence of  borates  in  many  fruits  must  not  be  overlooked  (see 
under  "Cider"). 

Adulterations. — The  adulterations  of  these  articles  are 
frequent  and  extensive.  Occasionally  no  true  fruit-ingredient, 
except  water,  is  present.  A  cheap,  so-called  strawberry  jam 
has  been  sold  consisting  of  apple  pulp,  glucose,  fuchsin,  sul- 
furic acid  (for  tartness),  grass  seed  (to  imitate  the  achenes  of  the 
fruit),  sodium  benzoate  and  artificial  flavors.  Apple  pulp  is 
frequently  used  as  a  basis,  also  starch  jelly.  Other  vegetable 
pectins,  such  as  agar,  may  be  used,  but  gelatin  has  not  been 
satisfactory.  Saccharin  or  other  artificial  sweetener  is  some- 
times used  in  complete  replacement  of  sucrose.  Saccharin 
may  also  be  present  merely  as  a  preservative. 

Analytical  examinations  will  include  particularly  tests  for 
ad(ied  color,  preservative,  glucose,  starch-jelly  and  artificial 
flavors.  The  determinations  of  ash,  total  solids,  proteids  and 
acidity  are  not  usually  important.  If  required  they  may  be 
made  by  the  standard  methods.  The  total  solids  will  be  best 
taken  by  making  a  definite  dilution  and  evaporating  this  on  a 
shallow  broad  glass  dish.  The  low-pressure  oven  (page  30) 
will  be  especially  suitable.  Added  color  is  to  be  sought  ac- 
cording to  the  methods  on  pages  64  to  75.  It  must  not  be  for- 
gotten that  at  present  several  natural  vegetable  colors  are  being 
used,  such  as  cochineal,  lichin  colors,  fustic  and  chlorophyl, 
hence  the  special  examinations  indicated  for  these  must  be  made 
in  addition  to  the  double-dyeing  test. 

Saccharin,  salicylic  acid,  benzoates  and  abrastol  are  detected 
by  acidulating  a  portion  of  the  sample  and  shaking  out  with 
the  mixture  of  petroleum  spirit  and  ether,  or  with  ether  alone. 
See  pages  86  and  362. 
29 


330  FOOD   ANALYSIS 

For  the  determination  of  glucose  see  page  1 26.  The  glucose 
used  in  the  articles  may  have  a  polarimetric  reading  of  150 
on  the  sugar  scale,  and  Leach's  formula  must  be  modified  as 
there  indicated. 

Lemon  Sirup. — This  is  a  mixture  of  lemon  juice  with  sugar. 
The  composition  of  samples  of  commercial  sirup  and  lemon 
juice  is  given  by  Borntraeger. 

Lemon  Juice 

Ripe  Fruit.        Unripe  Fruit. 

Citric  acid, 7.25  7.70 

Reducing  sugar, 0.75  0.2 1 

Sucrose, 0.19  0.78 

Ash, 0.39  0.49 

Total  solids, 8.87  9.30 

Lemon  Sirup 

Pure  Adulterated. 

Citric  acid, 14.40  5.42 

Tartaric  acid, 0.00  10.70 

Reducing  sugar  calculated  as  dextrose,.  .30.10  38.42 

Sucrose, 0.00  0.00 

Ash, 0.32  0.72 

Total  solids, 81 .92  80.56 

The  reducing  sugar  may  result  from  the  inversion  of  sucrose. 
The  price  of  tartaric  acid,  as  compared  with  citric,  leads  to 
the  use  of  the  former  in  imitation  sirups.  Other  acids,  such 
as  sulfuric,  may  be  used.  The  adulterations,  in  addition  to 
this  substitution,  will  be  similar  to  other  fruit  juices,  namely, 
imitation  coloring,  imitation  sweetening,  and,  possibly,  pre- 
servatives. The  methods  of  recognizing  these  additions  are 
described  in  the  section  on  "General  Methods"  and  under 
"Alcoholic  Beverages." 

Orange  juice  and  orange  sirup  will  be  subject  to  the  same 
adulterations  as  the  products  from  lemon,  and  are  to  be  tested 
in  the  same  way. 

Farnsteiner    &  Stueber  have  found  the  following  range  of 


FRUIT   JUICES,    SIRUPS,   JELLIES   AND   JAMS  33 1 

composition  in  orange  juice  known  to  be  pure.     The  figures 
are  grams  per  100  ex.,  except  as  noted. 

Total  solids, 10.73  10.92 

Citric  acid, 1.19  1.79 

Total  sugar  (after  inversion,  calculated  as  invert 

sugar), 7.65  8.26 

Ash, 0.41  0.52 

Alkalinity  of  ash  (c.c.  of          acid), 5.40  7.20 

Polarization, — o.  1 1  -f  2 .45 

There  were  small  amounts  of  proteids,  phosphates  and 
glycerol. 

The  artificial  flavors  employed  in  the  preparation  of  these 
articles  are  mostly  alcoholic  solutions  of  esters  of  acids  homol- 
ogous with  formic.  Ethyl  acetate  is  often  present  as  a  basis 
material;  pentyl  acetate  and  butyrate  are  common. 

Some  information  as  to  the  esters  present  in  a  sample  may 
be  obtained  by  fractional  distillation  in  an  apparatus  such 
as  shown  in  figure  29.  Several  fractions  should  be  collected, 
and  the  odor  of  each  carefully  noted.  The  esters  may  also 
be  saponified  by  strong  sodium  hydroxid  solution,  the  odor 
of  the  alcohol  produced  noted,  as  well  as  the  odor  of  the  acid 
obtained  by  decomposing  the  sodium  salts  with  sulfuric  acid. 

The  following  selection  from  published  formulas  for  arti- 
ficial flavors  will  show  the  general  characters  of  them.  The 
figures  are  the  relative  proportions  by  volume  to  100  parts 
of  alcohol  as  a  solvent. 

Pineapple:  chloroform,  i;  aldehyde,  i;  ethyl  butyrate,  5; 
pentyl  butyrate,  10. 

Strawberry:  ethyl  nitrite,  i ;  ethyl  acetate,  5 ;  ethyl  formate, 
i;  ethyl  butyrate,  5;  pentyl  butyrate,  2;  pentyl  acetate,  5. 

Raspberry:  ethyl  nitrite,  i;  aldehyde,  i;  ethyl  acetate,  5; 
ethyl  formate,  i;  ethyl  butyrate,  i;  ethyl  benzoate,  i;  ethyl 
enanthylate,  i ;  ethyl  sebacate,  i ;  methyl  salicylate,  i ;  pentyl 
acetate,  i ;  pentyl  butyrate,  i . 


332  FOOD   ANALYSIS 

Citric  acid  being  often  replaced  by  tartaric,  and  tartaric 
sometimes  substituted  by  cheaper  acids,  the  detection  of  the 
tartaric  and  the  determination  of  it  and  citric  acid  are  very 
important. 

Detection  oj  Tartaric  Acid.^^ — With  dry  materials,  mix  a 
little  of  the  sample  with  a  small  fragment  of  resorcinol,  then 
with  a  few  drops  of  sulfuric  acid  and  heat  slowly.  A  bright 
red  is  produced  with  tartaric  acid.  Fruit-juices  may  be  evapo- 
rated  to  dryness  and  the  residue  tested,  or  the  acid  potassium 
tartrate  may  be  precipitated  by  the  method  given  under  de- 
termination of  tartaric  and  this  precipitate  tested.  Starch 
must  not  be  present.     Phosphates  and  alkalies  do  not  interfere. 

Determination  of  Tartaric  Acid.^^ — loo  c.c.  of  the  fruit  juice 
are  mixed  with  2  c.c.  of  acetic  acid,  a  few  drops  of  a  20  per 
cent,  potassium  acetate  solution  and  15  grams  of  finely-pow- 
dered pure  potassium  chlorid  added,  shaken  until  the  mate- 
rials are  dissolved,  and  then  20  c.c.  of  alcohol  and  the  liquid 
stirred  actively  for  i  minute,  rubbing  the  walls  of  the  beaker 
with  the  glass  rod.  The  liquid  is  allowed  to  stand  for  15 
hours  at  room  temperature,  collected,  filtered  in  a  Gooch 
crucible  with  a  little  asbestos  felt,  using  a  filter  pump.  The 
washing  hquid  should  be  made  up  of  20  c.c.  alcohol,  100  c.c. 
water  and  15  grams  potassium  chlorid.  The  beaker  is  rinsed 
a  few  times  with  a  few  c.c.  of  this  solution  and  the  precipitate 
is  also  washed  with  some  of  it,  but  the  whole  amount  of  wash- 
ing liquid  used  should  not  be  more  than  20  c.c.  The  pre- 
cipitate and  filter  are  washed,  with  water,  back  into  the  beaker, 
brought  to  the  boiling  point,  and  while  hot  titrated  with  -^ 
sodium  hydroxid,  using  phenolphthalein.  To  the  amount  of 
alkali  used  15  c.c.  should  be  added  for  the  acid  tartrate  that 
is  not  precipitated,  i  c.c.  of  the  alkali  is  equivalent  to 
0.0075  gram  tartaric  acid.  Hardened  filters  might  replace  the 
filter  suggested. 

Determination  oj  Citric  Acid.^^ — 50  c.c.  of  the  juice  are  evapo- 


CATSUP,   TABLE   ACCESSORIES    AND   DESSERTS  333 

rated  on  the  water-bath  to  small  bulk.  Alcohol  is  added 
to  this  residue,  slowly  with  constant  stirring  until  no  further 
precipitation  occurs.  This  will  require  about  80  c.c.  The 
precipitate  is  collected  on  a  filter,  washed  with  alcohol,  evapo- 
rated until  the  alcohol  is  removed,  the  residue  taken  up  with 
water  and  made  up  to  10  c.c.  in  a  graduated  cylinder.  5  c.c. 
of  this  are  mixed  with  0.5  c.c.  acetic  acid,  and  then,  drop  by 
drop,  saturated  lead  subacetate  solution.  If  a  precipitate 
appears  which  is  dissolved  by  heating  and  reproduced  on 
cooling,  citric  acid  is  present.  Heat  the  liquid  to  boiling, 
filter  if  necessary,  wash  with  boiling  water.  On  cooling,  the 
lead  citrate  will  separate.  It  should  be  collected  on  a  hardened 
filter,  washed  into  weak  alcohol,  dried  and  weighed.  The 
weight  multipHed  by  0.385  will  give  citric  acid.  If  tartaric 
acid  is  present,  the  juice  must  be  neutralized  first  by  potas- 
sium hydroxid  in  order  to  prevent  the  precipitation  of  acid 
potassium  tartrate. 

TABLE    ACCESSORIES    AND    DESSERTS 

Very  many  articles  are  included  under  this  head,  mostly 
vegetable  products.  The  composition  of  them  is  given  in 
cook-books.  They  are  liable  to  adulteration  in  many  ways. 
The  basic  materials  may  be  imitated  by  cheaper  products, 
colors  and  preservatives  may  be  added.  It  must  not  be  for- 
gotten that  small  amounts  of  salicylates  and  borates  occur  in 
many  vegetable  substances,  and  further  that  some  of  the  basic 
material,  such  as  the  tomato-pulp  for  catsup,  may  be  mixed 
with  preservatives  by  the  wholesaler  in  order  to  keep  it,  and 
thus  small  amounts  be  found  in  the  finished  product,  although 
the  maker  of  the  latter  may  not  be  aware  of  it. 

For  the  ordinary  table  accessories,  the  methods  of  analysis 
will  be  directed  to  the  detection  of  added  color,  preservative 
and  in  some  cases  artificial  flavors  and  artificial  sweetening 
{e.  g.,  saccharin  and  glucose).     The  preservatives,  exclusive 


334  FOOD   ANALYSIS 

of  vinegar  and  common  salt,  are  usually  boric  acid,  salicylic 
acid  or  sodium  benzoate,  but  there  is  liability  to  the  use  of 
fluorids,  betanaphthol,  and  abrastol. 

Gelatin,  starch  and  agar  are  used  as  fillers.  Some  materials, 
e.  g.,  pickles  and  canned  peas,  are  liable  to  contain  small 
amounts  of  copper. 

The  methods  of  detection  of  most  of  these  ingredients  are 
given  elsewhere;  gelatin  and  agar  require  special  notice. 

Agar  (agar- agar)  is  derived  from  marine  alga?.  It  forms 
with  water  a  stiff  jelly  that  does  not  melt  as  readily  as  that 
from  gelatin.  If  is  used  as  a  thickening  agent  in  milk  and 
cream,  in  desserts  and  as  a  substitute  for  white  of  egg. 


Fig.  52. — Arachnoidiscus  Ehrenhergii.     X  loo-    The  smaller  oval  diatoms  are 
a  species  of  Cocconeis. 

Commercial  agar  almost  always  contains  diatoms.  One 
characteristic  form  is  Arachnoidiscus  Ehrenhergii.  (See  figure 
52.)  The  diatoms  may  be  obtained  by  oxidizing  the  organic 
material  with  a  mixture  of  nitric  and  sulfuric  acid  or  nitric 
and  hydrochloric  acids.  Moist  materials  should  be  well  dried 
but  not  powdered.  The  diatoms  will  be  found  by  examining 
the  residue  with  a  power  of  about  100  diameters. 

Gelatin. — For  the  detection  of  this  the  following  process  has 
been  proposed:  The  material  is  boiled  with  water,  filtered, 
the  filtrate  boiled  with  excess  of  potassium  dichromate,  cooled, 
and  a  few  drops  of  sulfuric  acid  added.  If  gelatin  is  present, 
a  flocculent  precipitate  will  be  formed. 


EGG- SUBSTITUTES  335 

It  is  probable  that  the  reaction  of  gelatin  with  formaldehyde 
could  be  utilized  in  these  examinations. 

Gelatin  in  mass  can  be  at  once  distinguished  from  starch 
and  agar  by  its  odor  on  heating  to  the  charring  point. 

Ice  Cream  and  Water  Ices  are  subject  to  adulteration  with 
starch,  gelatin  and  agar.  The  so-called  ''Hokey- Pokey" 
sold  in  slum  districts  is  usually  made  with  agar  on  account  of 
less  liabihty  of  the  jelly  to  melt.  This  and  similar  articles  are 
apt  to  be  unclean,  containing  bodies  of  insects  and  other  filth. 
Microscopic  examination  will  be  required  for  these.  The 
general  adulterations  above  enumerated  will  be  found  also. 
Formaldehyde  is  sometimes  used  in  ice  cream.  It  is  to  be  de- 
tected by  the  methods  given  under  milk. 

Cakes  and  Pastry  may  contain  fillers  (gelatin,  starch  and  agar), 
egg-substitutes,  sometimes  merely  color  to  simulate  egg-yolk. 
The  imitation  chocolate-paste  noted  on  page  64  is  often  used. 

For  special  processes  for  detection  of  eggs  see  under  "Egg- 
Substitutes." 
< 

EGG-SUBSTITUTES 

Several  forms  of  egg- substitutes  are  common.  Some  consist 
of  starch  and  sugar  with  coloring  matter;  others  contain  egg- 
albumin,  but  no  yolk.  Desiccated  eggs  are  now  a  commercial 
article.  These  may  have  added  color.  The  colors  commonly 
used  are  turmeric,  annatto,  and  coal-tar  dyes,  the  latter  being 
generally  azo-colors,  but  sometimes  nitro-colors. 

For  the  detection  of  colors  see  page  73.  The  recognition 
of  egg-yolk  as  an  ingredient  in  foods  has  been  investigated  by 
Winton  &  Bailey,^''  applying  especially  methods  of  Juckenack 
and  Pastenack,®*'  which  depend  on  determining  the  fat  and 
lecithin  of  the  egg-yolk.  The  lecithin  is  determined  in  the  form 
of  phosphoric  oxid.  For  the  determination  of  the  lecithin  phos- 
phorus, Winton  &  Bailey  recommend  Juckenack's  modifica- 
tion of  Wichelhaus'  method,  as  follows: 


33^  FOOD   ANALYSIS 

A  weighed  amount  (about  30  grams)  is  extracted  with  ab- 
sokite  alcohol  in  an  apparatus  so  arranged  that  the  material 
can  be  kept  not  lower  than  55°.  A  few  pieces  of  pumice  should 
be  put  in  the  flask  in  which  the  solvent  is  heated.  When  the 
extraction  seems  complete,  the  solution  should  be  saponified  by 
5  c.c.  of  a  4  %  solution  of  pure  potassium  hydroxid  in  alcohol. 
The  alcohol  is  distilled  off,  the  residue  transferred  to  a  platinum 
dish  by  aid  of  hot  water,  mixed  with  some  asbestos,  dried  on 
the  water-bath  and  charred.  The  char  is  treated  with  dilute 
nitric  acid,  filtered,  the  residue  washed  with  water  and  returned 
with  the  filter  paper  to  the  dish,  treated  again  with  nitric  acid, 
filtered,  the  filtrates  mixed  and  the  phosphoric  acid  determined 
in  the  usual  way.  It  is  principally  derived  from  the  lecithin  of 
the  egg-yolk. 

As  egg-yolk  contains  a  much  higher  percentage  of  fat  than 
flour,  the  ether-extract  of  many  food  articles  will  also  be  of 
value  in  determining  the  presence  of  eggs,  but  it  must  be  borne 
in  mind  that  to  many  articles,  milk,  butter  or  other  fats  are  added. 
The  following  data  are  from  a  compilation  by  Winton  &  Bailey 
of  the  original  results  of  Juckenack  &  Pastenack.  The  German 
pound  used  in  making  the  mixtures  is  about  468  grams.  The 
figures  are  percentages  of  phosphoric  oxid  and  ether-extract 
on  the  original  mixture. 

Phosphoric  Oxid.  Ether  Extract. 

Flour  with  no  eggs, 0.0225  °-^^ 

I  pound  flour  with  i  egg, 0.05 13  i  .56 

I  pound  flour  with  3  eggs, 0.1044  3.24 

I  pound  flour  with  12  eggs, 0.2875  7-94 

For  the  detection  of  azo-colors  in  pound  cake,  sponge  cake, 
and  similar  articles,  it  is  often  sufficient  to  touch  a  freshly- cut 
surface  with  hydrochloric  acid,  when  the  rose-pink  stain  will 
show  the  dye. 


CIDER 


337 


ALCOHOLIC  BEVERAGES 

CIDER 

Cider  is  the  juice  of  apples  either  before  or  after  ferment- 
ing; when  the  alcohol  is  in  considerable  amount,  the  liquid  is 
often  called  "hard  cider."  Cider  differs  from  wine  in  con- 
taining no  tartrates,  and  larger  amounts  of  malates  and  calcium 
compounds.  Pear  cider,  often  called  ''perry,"  contains  more 
sugar  than  apple  cider,  and,  therefore,  yields  more  alcohol  when 
fully  fermented.  Many  other  fruits  will  yield  fermentable 
juices  more  or  less  analogous  to  true  cider. 

The  following  analyses  by  Browne °^  show  the  range  of  com- 
position of  fresh  and  fermented  apple  juices.  The  figures  are 
grams  per  loo  c.c. 

Apple  Juice.  Fermented  Juice. 

Total  solids, 1 1 .36-16.85  i  ,93-3.26 

Invert  sugar, 5.47-10.52  0.19-0.89 

Sucrose, i  .83-  7.05 

Free  malic  acid, o.io-  1.24  0.21-0.30 

-  'Ash, 0.23-  0.37  0.23-0.36 

Acetic  acid, ..  0.21-1.96 

Alcohol, . .  4.26-6.85 

Fresh  apple  juice  is  always  strongly  levorotatory,  and  retains 
some  of  this  power  after  fermentation  and  even  after  conversion 
into  vinegar.  Several  observers  have  shown  the  presence  of 
borates  in  fruits.  The  following  data  were  obtained  by  Allen  & 
Tankard  ®*  by  the  method  given  in  connection  with  the  analysis 
of  alcoholic  beverages. 

Per  Cent.  Orthoboric  Acid. 

Apple, 0.009-0.013 

Pear, 0.007-0.016 

Quince, 0.016 

Pomegranate, 0.005 

Grapes, 0.004 

Cider, 0.004-0.017  grams  per  100  c.c. 

30 


338  FOOD   ANALYSIS 

The  provisional  standards  for  cider  offered  by  the  A.  O.  A.  C. 
are: 

Alcohol, not  over  8.0  per  cent. 

Ash, not  less  than  0.2        " 

Apple  solids, "     "        "      1.8       " 

Adulterations. — The  usual  adulterations  of  cider  are 
dilution  with  water,  addition  of  sodium  carbonate  or  lime  in 
order  to  correct  acidity,  and  addition  of  preservatives.  The 
ash  of  cider  contains  no  sodium.  When  heated,  it  volatilizes 
at  a  comparatively  low  temperature,  and  imparts  to  flame  a 
pure  potassium  color.  The  dilution  of  cider  with  ordinary 
water  containing  even  a  small  proportion  of  sodium  may  be 
detected  by  this  test.  The  proportion  of  ash  to  the  original 
solids  may  furnish  some  indication  of  the  nature  of  a  sample 
under  examination.  In  unfermented  cider  the  ash  will  range 
from  2  to  5  per  cent,  of  the  total  solids.  If  the  sample  be  fer- 
mented, an  allowance  must  be  made  for  the  loss  in  solids.  (See 
under  ''Cider  Vinegar.")  Caramel  or  coal-tar  colors  may  be 
present  in  dilute  samples.  Sodium  carbonate  may  be  added  to 
diminish  acidity.  It  will  appear  in  the  ash.  Preservatives 
are  often  used,  the  most  frequent  being  salicylic  acid,  sulfites, 
sodium  benzoate  and  formaldehyde.  The  natural  occurrence 
of  borates  in  small  amount  must  not  be  overlooked. 

The  analysis  of  cider  is  conducted  by  the  methods  given  for 
alcoholic  beverages. 

SPIRITS 

Spirits  are  the  Hquors  obtained  by  the  distillation  of  alcoholic 
liquids.  The  latter  are  the  results  of  fermentation  of  saccha- 
rine infusions  derived  from  barley,  oats,  wheat,  maize,  rice, 
potatoes,  or  from  vegetable  juices.  The  distilled  liquor  con- 
tains water,  ethyl  alcohol  along  with  a  small  proportion  of  its 
homologues  (fusel  oil),  aldehydes,  acetic  acid,  and  various 
esters.     The  amount  and    nature  of  these  associated  bodies 


WHISKEY  339 

depend  upon  the  nature  of  the  fermented  material  and  the 
method  of  manufacture.  The  character  of  the  distilled  spirit 
is  further  modified  by  the  addition  of  various  flavoring  mate- 
rials. 

WHISKEY 

Whiskey  is  the  spirit  distilled  from  fermented  grain  or  po- 
tatoes. In  some  cases  malted  grain  is  used,  but  more  usually 
a  mixture  of  malted  and  unmalted  grain  is  employed.  Spirit 
from  raw  grain  usually  contains  a  larger  proportion  of  fusel  oil. 
The  grain  commonly  employed  in  the  United  States  is  rye  and 
maize,  but  wheat  is  also  used  to  a  considerable  extent  and  glu- 
cose is  a  frequent  addition.  The  weak  spirit  (so-called  "low 
wine")  which  is  obtained  by  distillation  is  usually  redistilled,  by 
which  it  is  obtained  stronger  and  less  charged  with  fusel  oil. 
When  only  malted  grain  is  used,  the  liquid  is  sometimes  distilled 
in  small  stills,  called  "pot  heads,"  and  at  once  set  aside  to  age 
without  redistillation. 

Freshly  distilled  whiskey  is  colorless  and  of  disagreeable 
flavor.  It  is  often  stored  in  sherry  casks,  and  allowed  to  remain 
for  a  considerable  time  until  it  has  aged  or  ripened,  the  pro- 
cess consisting  in  part  in  the  conversion  of  the  fusel  oil  into 
various  esters  of  agreeable  smell  and  taste.  At  the  same  time 
a  small  amount  of  tannin  and  other  matters  are  extracted  from 
the  cask,  and  the  whiskey  acquires  an  amber  or  yellow  color, 
which  is  frequently  heightened  by  the  addition  of  caramel, 
logwood,  catechu,  tea  infusions  and  prune  juice.  Old  whiskey 
has  an  acid  reaction,  due  to  the  presence  of  a  small  amount  of 
acetic  and  possibly  other  acids.  The  acidity  increases  with 
age,  but  is  rarely  over  o.i  per  cent,  expressed  as  acetic  acid. 

The  U.  S.  Pharmacopeia^®  defines  whiskey  to  be  "a  distillate 
from  the  mash  of  fermented  grain,  as  maize,  wheat,  or  rye.  It 
is  an  amber-colored,  slightly  acid  liquid.  The  specific  gravity 
should  be  not  more  than  0.930  nor  less  than  0.917,  corresponding 


340  FOOD   ANALYSIS 

to  an  alcoholic  strength  of  from  44  to  50  per  cent,  by  weight 
or  50  to  58  per  cent,  by  volume.  If  100  c.c.  be  slowly  evaporated 
in  a  tared  capsule  in  a  steam-bath,  the  last  portion  should  not 
have  a  harsh  or  disagreeable  odor  (absence  of  more  than  mere 
traces  of  fusel  oil).  The  residue,  dried  at  100°,  should  not 
weigh  more  than  0.21  gram,  have  no  sweet  or  distinctly  spicy 
taste,  should  dissolve  almost  completely  in  10  c.c.  of  cold  water 
to  form  a  solution  not  more  deeply  colored  than  light  green  by  a 
few  drops  of  ferric  chlorid  solution  (absence  of  more  than  traces 
of  oak  tannin).  100  c.c.  of  whiskey  should  not  require  more 
than  12  c.c.  ^  sodium  hydroxid  to  render  it  distinctly  alka- 
line." 

In  Scotland  and  Ireland  the  drying  of  the  malt  takes  place 
in  kilns  in  which  peat  is  used  as  fuel,  and  the  spirit  whiskey 
made  from  it  has  a  strong  smoky  flavor.  This  is  often  im- 
itated by  the  addition  of  two  drops  of  creasote  to  the  gallon  of 
spirits.  A  variety  of  whiskey  is  sometimes  made  by  distilling 
cider,  and  is  known  as  apple- whiskey  or  apple-brandy. 

Whiskey  is  occasionally  adulterated  with  methyl  alcohol. 
Cayenne  pepper  is  also  said  to  be  added  in  order  to  give  greater 
warmth  of  taste,  and  thus  enable  a  weak  spirit  to  be  sold  for  a 
strong  one.  In  some  cases  it  appears  to  have  been  added 
simply  as  a  flavor. 

Lead,  copper,  and  zinc  have  been  found  in  whiskey,  and  are 
probably  derived  from  the  apparatus  employed  in  the  dis- 
tillery.    They  are  also  said  to  have  been  added  directly. 

The  following  are  some  results  of  analyses  of  commercial 
whiskey  by  Allen: 

Commercial         Commercial 
Scotch  Whiskey.  Irish  Whiskey. 

Specific   gravity, 0.9416  0.9408 

Alcohol  (percentage  by  weight), 39-05  '39-3° 

Secondary  constituents,  expressed  in  grains 
per  imp.  gallon: 

Free  acid,  as  acetic, 10.2  6.8 

Ethers  in  terms  of  acetic  ether, 46.5  23.1 

Higher  alcohols  in  terms  of  amyl  alcohol,  89.6  78.8 

Aldehyde, Trace.  Trace. 

Furfural, " 


BRANDY — GIN — RUM  34 1 

BRANDY 

Brandy,  also  called  French  brandy  or  ''cognac,"  is  the 
spirit  obtained  by  distilling  wine.  An  inferior  quality  is 
manufactured  from  skins  and  stalks  ("marc")  of  the  grapes. 
Such  brandy  usually  contains  more  fusel  oil  than  that  made 
from  wine.  So-called  British  brandy  is  made  from  grain 
spirit  to  which  is  added  flavoring  esters,  such  as  ethyl  acetate, 
pelargonate  and  nitrate,  bitter  almonds,  spices,  and  caramel. 
Freshly  distilled  brandy  is  colorless,  but  on  standing  in  casks 
it  dissolves  a  minute  quantity  of  tannin  and  other  bodies  and 
acquires  an  amber  tint.  It  is  also  frequently  colored  with 
caramel. 

The  provisional  standard  of  A.  O.  A.  C.  for  brandy  is: 

Alcohol  by  volume, 44-55  per  cent. 

Total  solids, not  over   0.35         " 

GIN 

Gin,  and  the  varieties  known  as  Hollands  or  Schnapps,  are 
usually  prepared  by  redistilling  grain  spirit  which  has  been 
flavored  with  various  bodies,  among  which  may  be  mentioned 
juniper  berries  or  oil  of  juniper,  turpentine,  coriander  and  car- 
damon  seeds,  capsicum,  orris,  angelica,  and  calamus  roots. 
Gin  is  without  color  and  is  comparatively  free  from  fusel  oil 
and  the  associated  bodies  found  in  brandy  and  whiskey. 

The  A.  O.  A.  C.  standard  requires  not  less  than  40  per  cent, 
of  alcohol  by  volume. 

RUM 

Rum  is  the  spirit  obtained  by  distilling  the  fermented  juice 
of  the  sugar-cane,  or,  more  commonly,  by  distilling  fermented 
molasses.  The  flavor  of  rum  is  due  largely  to  the  presence 
of  ethyl  butyrate  and  ethyl  formate.  It  is  colored  either  by 
long  keeping  in  casks,  or  by  the  addition  of  burnt  sugar.  Much 
of  the  commercial  article  is  made  from  grain  spirit  to  which 


342  FOOD   ANALYSIS 

has  been  added  butyric  acid  or  butyric  or  acetic  esters.  Pine- 
apple and  tannin-containing  materials  are  also  added.  Ac- 
cording to  Allen,  the  presence  of  formates  might  serve  to 
distinguish  genuine  rum  from  the  factitious  product.  The 
rum  should  be  evaporated  almost  to  dryness  with  a  slight 
excess  of  sodium  hydroxid  and  the  residue  treated  with  phos- 
phoric acid  and  distilled.  The  distillate  from  genuine  rum 
will  strongly  reduce  silver  nitrate,  and  give  the  other  reactions 
for  formic  acid. 

The  A.  O.  A.  C.  standard  for  rum  gives  a  range  of  alcohol 
by  volume  from  44  to  55  per  cent. 

MALT  LIQUORS 

These  are,  strictly  speaking,  infusions  of  malt,  fermented 
by  yeast,  and  rendered  bitter  by  the  addition  of  hops.  Hop- 
substitutes  are  little  used  unless  the  price  of  hops  advances, 
when  quassia,  chiretta,  and  aloes  may  be  employed.  The 
common  substitutes  for  malt  are  unmalted  cereals,  glucose, 
and  starch. 

Two  methods  of  fermentation  are  in  use  for  the  prepara- 
tion of  beers.  The  "high"  or  ''surface"  fermentation,  em- 
ployed for  English  beers,  takes  place  at  a  temperature  of  15° 
to  20°,  and  is  completed  in  from  4  to  8  days.  The  "low" 
or  "bottom"  fermentation,  employed  in  Germany,  takes 
place  at  a  temperature  of  from  4°  to  8°,  and  requires  from 
20  to  24  days  for  completion.  In  this  process  the  yeast 
remains  at  the  bottom  of  the  vat.  In  each  of  these  there  is 
a  predominance  of  particular  species  of  yeasts,  and  unless 
carefully  selected  and  cultivated,  the  yeast  mass  will  contain 
species  producing  irregular  and  often  objectionable  fermenta- 
tion-products. In  this  way  malt  liquors  may  acquire  unpleas- 
ant bitterness  or  odor,  or  troublesome  turbidity. 

The  principal  constituents  of  beer  are  as  follows: 

Volatile. — Water,  alcohol,  acetic  and  other  acids. 


MALT  LIQUORS  343 

Fixed. — (Extract.)  Sugar,  chiefly  maltose,  dextrin,  and 
similar  bodies,  proteids,  glycerol,  lactic  acid,  succinic  acid, 
bitter  principles,  and  mineral  matters,  chiefly  phosphates. 

The  following  are  the  principal  varieties  of  malt  liquors: 

Ale,  made  from  a  light-colored  malt,  usually  with  addition 
of  glucose,  and  a  large  proportion  of  hops.  So-called  ''mild 
ales"  are  usually  sweeter,  contain  a  larger  proportion  of 
alcohol,  and  are  less  bitter. 

Porter  and  Stout  are  principally  distinguished  from  the 
above  by  their  flavor,  derived  from  the  use  of  a  certain  pro- 
portion of  roasted  malt.     They  also  contain  less  hops. 

Ale,  porter,  and  stout  are  made  by  the  high  fermentation 
process.  Lager  or  German  Beer  is  prepared  by  the  low 
fermentation  process  and  contains  less  alcohol,  more  sugar, 
dextrin,  and  nitrogenous  matter,  and  is  more  highly  charged 
with  gas.  Lager  beers  are  liable  to  undergo  a  second  fer- 
mentation unless  kept  at  a  low  temperature. 

So-called  Weissbier  is  light-colored  and  about  half  the 
strength  of  lager  beer.  Rice  is  often  used  in  its  manufac- 
ture. 

Root  Beers  and  Meads. — Solutions  of  cane-sugar  flavored 
with  herbs  and  roots  are  much  used  for  the  manufacture  of 
home-brewed  beers.  These  are  subjected  to  a  brief  fermenta- 
tion in  closed  vessels,  and,  as  a  rule,  but  insignificant  propor- 
tions of  alcohol  are  formed. 

Adulteration. — The  chief  adulteration  of  malt  liquors 
consists  in  the  addition  of  substances  other  than  malt  and  of 
preservatives.  The  use  of  glucose  is  very  common,  and  may 
pDSsibly  be  detected  by  the  presence  of  gallisin,  which  is  a 
usual  constituent  of  the  commercial  article.  The  substitu- 
tion of  any  considerable  proportion  of  glucose,  rice,  or  starch 
for  the  barley  will  be  indicated  by  the  lowered  proportion  of 
proteids,  ash,  and  phosphates.  Glucose  is  especially  indicated 
by  high  proportion  of  sulfates  to  total  ash. 


344 


FOOD   ANALYSIS 


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WINE  345 

The  addition  of  preservatives,  especially  salicylic  acid, 
sodium  fluorid,  sodium  silicofluorid,  and  of  sulfites  is  very 
common.  Sodium  bicarbonate  is  also  added  in  order  to  cor- 
rect acidity.  The  quantity  of  chlorids  may,  at  times,  be  con- 
siderable, due  either  to  the  addition  of  salt,  or  to  the  presence 
of  chlorids  in  the  water  used  in  making  the  mash.  The  direct 
addition  of  salt  is  probably  infrequent. 

The  following  recommendations  as  to  standards  of  composi- 
tion of  beer  were  made  in  1897  to  the  Association  of  Official 
Agricultural  Chemists  by  the  referee  on  food  adulteration: 

"The  glycerol  content  of  beer  should  not  be  less  than  0.4 
gram  per  100  c.c.  The  ash  should  not  be  less  than  0.12  nor 
greater  than  0.30  gram  per  100  c.c.  The  presence  of  less  than 
o.io  gram  indicates  that  some  malt  substitute  low  in  ash,  such 
as  starch,  has  been  used  in  the  preparation  of  the  beer,  while 
if  the  ash  content  be  greater  than  0.30  gram  per  100  c.c,  and 
the  volatile  acids,  calculated  to  acetic  acid,  less  than  0.075  gram 
per  100  c.c,  it  is  probable  that  an  excess  of  acid  has  been  neu- 
tralized by  sodium  carbonate,  and  the  ash  of  the  beer  should 
be  examined  for  both  sodium  and  carbonic  acid.  The  phos- 
phoric oxid  should  not  be  less  than  0.05  gram  nor  greater  than 
0.10  gram  per  100  c.c.  If  less  than  0.05  gram,  it  is  probable 
that  a  portion  of  the  malt  has  been  replaced  by  starch  or  similar 
substance." 

WINE 
Wine  has  been  defined  to  be  the  fermented  juice  of  the  grape 
with  such  additions  as  are  essential  to  the  stability  or  keeping 
of  the  liquid.  The  method  of  preparation  is,  briefly,  as  follows: 
The  grapes  are  crushed,  the  stem  being  removed  in  the  case 
of  the  better  grades  of  wine,  and  the  juice  expressed.  The 
juice  or  ''must"  is  sometimes  allowed  to  stand  in  contact  with 
the  skins  for  several  days  in  order  to  extract  additional  ''bou- 
quet."    In  the  case  of  red  wines,  the  expression  of  the  juice 


346  FOOD   ANALYSIS 

and  removal  of  the  skins  do  not  take  place  until  the  fermentation 
is  practically  completed.  The  juice  of  most  varieties  of  grapes 
is  colorless,  but  in  the  presence  of  alcohol  formed  by  the  fer- 
mentation the  red  coloring-matter  of  the  skin  is  extracted;  red 
wine  contains  a  greater  proportion  of  tannin  than  white  wine. 
The  chief  fermentation  of  the  wine  usually  takes  place  in  from 
four  days  to  several  weeks,  according  to  the  temperature  at 
which  it  is  conducted.  After  this,  the  liquid  is  drawn  off  into 
casks,  where  a  secondary  quiet  fermentation  takes  place. 
The  wine  is  then  allowed  to  age  or  ripen,  a  process  which  in- 
volves chiefly  direct  oxidation,  and  during  which  potassium 
acid  tartrate  is  deposited,  along  with  a  considerable  proportion 
of  the  coloring-matter,  and,  by  the  interaction  of  the  alcohols 
with  the  acids  and  other  constituents  present,  various  esters 
are  formed  which  give  flavor  and  bouquet. 

The  yeast  that  ferments  the  must  is  found  on  grape  skins. 
There  are  many  varieties,  some  of  which  produce  special  flavors, 
and  by  the  application  of  these  in  special  cases  the  flavor  of  the 
wine  may  be  modified. 

Wines  prepared  as  above  usually  contain  very  little  sugar, 
and  are  termed  dry  wines,  as  distinguished  from  "full-bodied" 
or  sweet  wines.  Some  wines  are  prepared  by  adding  to  the 
must  a  certain  proportion  of  alcohol,  which  causes  the  fermenta- 
tion to  cease  before  the  complete  conversion  of  the  sugar  is 
effected.     Port  and  sherry  are  manufactured  in  this  way. 

Champagne  is  usually  prepared  as  follows:  The  pressed 
grapes  are  fermented  as  rapidly  as  possible  until  but  little 
sugar  is  left.  The  clarified  wine  is  blended  with  other  wine 
to  bring  it  to  the  quality  desired,  and  pure  sugar  (about  2  per 
cent.)  is  added  and  the  liquid  placed  in  strong  bottles,"  which 
are  tightly  stoppered  and  placed  horizontally  until  fermenta- 
tion is  completed,  and  then  with  the  necks  downward,  and, 
as  the  wine  clarifies,  the  yeast- sediment  collects  on  the  stop- 
per.    This  is  promoted  by  frequent  turning  and  manipula- 


WINE  347 

tion  of  the  bottle.  The  bottle  is  then  skilfully  uncorked  and 
a  small  portion  of  the  wine,  carrying  with  it  the  sediment, 
removed.  The  space  so  emptied  is  filled  by  the  addition  of 
wine  and  a  certain  proportion  of  so-called  liqueur,  and  the 
bottle  recorked  and  wired.  The  operations  are  performed 
so  quickly  that  there  is  but  little  loss  of  carbon  dioxid.  The 
liqueur  consists  of  a  mixture  of  sugar,  wine,  and  cognac.  Cham- 
pagne is  sometimes  prepared  by  adding  the  liqueur  to  the  fer- 
mented wine  and  charging  the  liquid  with  carbon  dioxid  under 
pressure. 

The  normal  constituents  of  wine  are  water,  alcohol  and  its 
homologues,  acetic  acid,  succinic  acid,  various  compound 
ethers,  sugar,  gum,  pectin,  glycerol,  tannin,  coloring-matters 
(in  red  wine),  tartaric  acid,  calcium  or  potassium  tartrates, 
phosphates,  and  other  mineral  matter. 

The  sugar  in  wine  is  apt  to  be  chiefly  levulose,  dextrose 
being  more  readily  fermentable. 

The  table  on  page  348  gives  the  composition  of  must  and 
wines  from  various  sources  expressed  in  grams  per  100  c.c. 
The  data  are  derived  in  most  cases  from  the  examination  of  a 
great  many  samples. 

Adulteration. — The  fact  that  the  composition  of  wine 
varies  within  notable  limits  renders  it  impossible  to  assign  ab- 
solute standards  and  allow  a  margin  for  the  addition  of  water 
and  other  substances  without  so  far  changing  the  composition 
as  to  enable  the  chemist  to  determine  whether  a  given  sample 
is  or  is  not  genuine.  Usually  it  can  only  be  stated  that  the 
sample  conforms  in  composition  to  that  of  genuine  wine. 

In  some  cases  additions  to  the  wine  or  must  are  regarded 
as  legitimate.  Thus,  it  has  been  found  that  a  certain  propor- 
tion of  acid  to  sugar  in  the  must  is  best  adapted  to  the  pro- 
duction of  good  wine;  and  in  cases  in  which  this  proportion 
does  not  obtain,  it  is  the  practice,  in  some  localities,  to  make 
such  additions  as  are  necessary  to  bring  these  constituents 
within  the  proper  limits. 


348 


FOOD   ANALYSIS 


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349 


The  following  conclusions  were  arrived  at  by  an  official 
German  commission: 

The  total  extract  of  wines  should  not  be  below  1.5  grams 
per  100  ex.  After  deducting  the  non-volatile  acids,  the  ex- 
tract should  be  at  least  i.i  grams  per  100  c.c. 

Natural  wines  usually  contain  a  close  approximation  of  i 
part  ash  to  10  parts  of  extract. 

The  proportion  of  free  acid  calculated  as  tartaric  acid  ap- 
pears not  to  exceed  one-sixth  of  the  total  volatile  acid. 

Genuine  wines  will  not  contain  less  than  0.14  gram  of  ash 
nor  more  than  0.05  gram  of  sodium  chlorid  in  100  c.c. 

U.  S.  Standard. 

Alcohol  by  volume 7  to  10  per  cent. 

Sodium  chlorid,  not  over o.i      gram  in   100  c.c. 

Potassium  sulfate,  not  over    ...0.2         **      ''         '* 

Volatile     acids  ^  ^    ,     . 

,     ,  ,   ,  Red  wme 0,14   gram  to   100  c.c. 

calculated  as  V  .  ,,      ,, 

I  White  wme.. 0.1 2       "      '' 
acetic  ) 

Dry  Wine. 

Sugar,  less  than i.o       gram  in   100  c.c. 

Grape  solids,  red  wine,  not  less 

than 1.6  ''       " 

Grape   solids,  white  wine,  not 

less  than    1.4  ''       '' 

Grape  ash,  red  wine,  not  less 

than   0.16 

Grape  ash,  white  wine,  not  less 

than   0.13 

Sweet  wine. 

Sugars,  not  less  than i.o  "       ** 

Grape  ash,  red  wine,  not  less 

than   0.16        ''       " 

Grape  ash,  white  wine,  not  less 

than   0.13        ''       " 


350  rOOD   ANALYSIS 

The  plastering  of  wines  consists  in  sprinkling  the  grape  or 
must  with  plaster-of- Paris,  with  a  view  of  securing  a  quicker 
fermentation,  better  color,  and  keeping  quahties.  Plastered 
wine  shows  but  a  small  increase  in  ash,  but  the  wine  from 
plastered  must  shows  a  large  increase  in  the  form  of  potas- 
sium sulfate  rather  than  calcium  sulfate.  If  a  wine  unusually 
rich  in  sulfates  and  potassium  compounds  contains  little  or 
no  tartar,  it  must  have  been  plastered,  and  the  absence  of  alka- 
linity in  the  ash  will  confirm  this. 

Sulfurous  acid  is  often  present  in  new  wines,  from  the  use  of 
sulfites  or  burning  sulfur  for  the  purpose  of  disinfecting  the 
casks. 

The  additions  to  wine  commonly  practised  are  sugar,  glu- 
cose, honey,  glycerol,  tartaric  acid  and  other  vegetable  acids, 
gums,  tannin,  vegetable  astringents,  coloring-matters,  flavor- 
ing ethers,  salicylic  acid  and  other  preservatives.  In  order  to 
increase  the  sugar,  total  extract  and  free  acid,  figs,  dates,  tama- 
rinds, and  St.  John's  bread  are  frequently  employed.  Dried 
raisins  are  largely  used  for  the  manufacture  of  imitation  wines. 

A  form  of  adulteration  is  the  decolorization  of  red  wine  by 
the  use  of  charcoal  or  possibly  potassium  permanganate,  the 
product  being  sold  as  a  genuine  white  wine.  Astruc  made 
a  number  of  experiments  on  the  effect  of  decolorizing  by 
means  of  various  forms  of  charcoal,  including  crude  and  puri- 
fied bone-black,  lamp-blacks,  and  vegetable  charcoal.  All 
the  decolorizers  absorbed  a  little  alcohol  (0.4  to  1.5  per  cent. 
of  a  total  of  7.8);  a  small  proportion  of  the  total  acidity;  0.5 
to  2.65  per  cent,  of  the  glycerol  (out  of  a  total  of  4.5  per  cent.); 
and  0.95  to  2.65  per  cent,  out  of  a  total  of  3.45  per  cent,  of  tannin, 
besides  extracting  the  coloring-matter.  The  crude  bone-blacks 
are  distinguished  from  the  purified  blacks  and  vegetable  char- 
coals by  the  fact  that  the  former  remove  almost  the  whole  of 
the  tartrates  and  a  larger  proportion  of  glycerol,  and  double 
the  proportion  of  mineral  matter  in  solution,  the  increase  being 


WINE  351 

entirely  in  soluble  ash  constituents  (chiefly  calcium  phosphates), 
whereas  the  soluble  portion  is  diminished.  The  decolorizing 
power  of  the  vegetable  blacks  is  low  and  a  much  larger  quantity 
is  required,  the  effect  of  which  on  the  chemical  constitution  is 
greater  than  that  of  a  suitable  amount  of  bone-black. 

The  following  is  an  analysis  by  Hougounenq  of  a  white 
wine  supposed  to  have  been  prepared  from  red  wine  by  the 
addition  of  potassium  permanganate  and  charcoal : 

Alcohol, 7.13  per  cent. 

Extract  (in  vacuo), 22.27  grams  per  liter. 

Ash, 3.59 

Alkalinity  of  ash  as  potassium  carbonate, .    i .  1 6 

Potassium  sulfate, 1.14 

Acidity,  total,  as  sulfuric  acid, 4.25 

"         volatile,  as  acetic  acid,    1.23 

Reducing  substances  as  glucose, 1.47 

Glycerol, i  .07 

The  ash  was  red  and  porous.  The  sample  contained  0.59 
gram  of  manganous  oxid  per  liter. 

Analyses  of  pure  Ohio  wines  by  Smith  &  Parks  are  of  interest 
as  indicating  a  composition  in  some  respects  different  from 
European  wines.  The  average  of  solids  is  slightly  lower  than 
that  of  foreign  wines,  but  the  most  important  differences  are 
the  percentages  of  glycerol  and  ash.  Published  reports  from 
European  samples  give  ash  usually  above  o.i  per  cent.,  and  from 
0.5  to  0.8  per  cent,  of  glycerol,  while  the  maximum  and  mini- 
mum found  with  the  Ohio  samples  are  0.15  to  o.io  for  ash,  and 
0.95  and  0.29  for  glycerol.  Since  these  two  constituents,  to- 
gether with  the  solids,  are  of  much  value  in  determining  the 
genuineness  and  purity  of  a  sample  of  wine,  the  differences  are 
most  important.  Many  authorities  state  that  in  the  natural 
process  of  alcoholic  fermentation,  glycerol  and  alcohol  are  pro- 
duced in  the  ratio  of  from  7  to  14  parts  of  the  former  to  100 
parts  of  the  latter,  from  which  would  be  drawn  the  inference, 
when  this  maximum  is  exceeded,  that  glycerol  has  been  added; 


352  FOOD   ANALYSIS 

while  in  case  the  ratio  of  glycerol  to  alcohol  is  below  7  :  loo, 
the  inference  would  be  drawn  that  the  sample  has  been  fortified 
by  the  addition  of  alcohol.  Such  conclusions  in  the  case  of 
Ohio  wines  would  be  quite  misleading.  Smith  &  Parks  also 
call  attention  to  the  fact  that  care  must  be  exercised,  when 
these  wines  are  under  consideration,  in  drawing  conclusions 
as  to  the  addition  of  water  from  the  fact  of  low  ash  and  solids. 
Appreciable  amounts  of  copper,  zinc,  lead,  and  arsenic  are 
occasionally  found  in  wine.  These  are  probably  introduced 
along  with  crude  glucose,  anilin  colors,  or  other  materials  which 
have  been  added.  Lead  has  been  introduced  by  the  use  of 
bottles  that  have  been  cleaned  with  shot. 

Analytic  Methods. 

For  the  detection  of  alcohol  when  present  in  very  small  amount 
several  tests  have  been  devised,  but  the  reactions  are  produced 
by  other  substances.  The  following  are  the  most  satisfactory. 
They  should  be  applied  to  samples  containing  no  active  in- 
gredients but  water  and  alcohol;  ordinary  mixtures  should, 
therefore,  be  distilled  and  the  distillate  tested. 

Hardy^s  Test. — A  small  quantity  of  powdered  guaiacum 
resin  taken  from  the  interior  of  a  lump  is  shaken  with  a  few 
c.c.  of  the  sample,  the  liquid  filtered,  and  a  few  drops  of  hy- 
drogen cyanid  solution  and  a  drop  of  very  dilute  copper  sul- 
fate solution  added.  In  the  presence  of  alcohol  a  blue  tint 
much  deeper  than  that  due  to  the  copper  sulfate  will  appear. 

Merck's  Modification  oj  Davy's  Test. — Pure  molybdenum 
trioxid  is  dissolved  in  warm  sulfuric  acid,  and  the  mixture 
poured  through  the  solution  to  be  tested,  keeping  the  mass  as 
near  as  possible  at  60°.  Alcohol  produces  a  blue  ring  at  the 
junction  of  the  liquids. 

Hager's  Modification  oj  Lichen'' s  Test. — 10  c.c.  of  the  sample 
are  mixed  with  5  drops  of  a  10  per  cent,  solution  of  sodium 
hydroxid    and   the    liquid   heated   to    about    50°.     Potassium 


WINE  353 

iodid-iodin  solution  is  added  drop  by  drop  with  shaking  until 
the  liquid  is  permanently  yellowish-brown.  It  is  then  de- 
colorized by  the  cautious  addition  of  more  sodium  hydroxid. 
If  alcohol  is  present,  iodoform  will  be  produced  as  a  yellow 
precipitate  of  characteristic  odor  and  crystalline  form.  Under 
rather  high  magnifying  power  (200  diameters)  these  are  seen 
to  consist  of  hexagonal  plates  or  six-pointed  stars.  This  is  a 
good  test,  but  requires  care.  The  iodin  solution  should  be 
strong  and  the  directions  should  be  followed  closely.  The  re- 
action is  given  by  many  bodies,  but  not  by  methyl  alcohol,  fusel 
oil,  common  ether,  chloral,  chloroform,  or  glycerol. 
Determination  oj   Alcohol. 

Specific  gravity  determinations  of  commercial  liquors  are 
made,  but  the  figures  have  little  practical  bearing. 

Alcohol  may  be  determined  directly  in  spirits  and  other  mix- 
tures containing  but  little  solid  matter  by  taking  the  specific 
gravity  and  correcting  for  temperature.  This  is  the  method 
used  by  revenue  officers. 

For  determining  the  alcohol  in  samples  containing  appre- 
ciable amounts  of  solid  matters,  several  methods  have  been 
devised,  of  which  only  two  deserve  mention  here:  distilla- 
tion and  observation  of  boiling-point. 

For  distillation  200  c.c.  of  the  sample  should  be  taken,  100 
c.c.  of  water  added,  the  mixture  distilled  until  200  c.c.  are 
collected.  The  specific  gravity  of  this  is  taken  at  standard 
temperature  and  the  percentage  of  alcohol  ascertained  by  the 
annexed  tables. 

The  tables  here  given  are  condensed  from  those  recalculated 
by  Edgar  Richards  from  the  determinations  of  Gilpin,  Drink- 
water  and  Squibb,  and  published  by  the  A.  O.  A.  C.  All  data 
are  given  at  Y"^].  The  figures  in  columns  designated  volume 
(V)  or  weight  (W)  are  the  percentage  of  absolute  alcohol,  by 
volume  or  weight  respectively,  corresponding  to  the  specific 
gravity  indicated.  When  the  percentage  in  two  lines  is  the 
31 


354 


FOOD   ANALYSIS 


Speci- 

Speci- 

Speci- 

Speci- 

fic 
Grav- 

Vol- 
ume. 

Weight 

fic 

(iRAV- 

Vol- 
ume 

Weigh -I 

fic 
Grav- 

Vol 

UME. 

Weight 

fic 
Grav- 

Vol- 
ume 

Weight 

ity. 

ITY. 

ity. 

ity. 

I.OOOO 

0.0 

0.0 

0.9928 

50 

4.0 

0.9866 

lO.O 

8.0 

0.981 1 

150 

12. 1 

0.999a 

I 

0 

26 

I 

0 

64 

I 

I 

ID 

1 

2 

96 

2 

I 

25 

2 

I 

63 

2 

2 

09 

2 

2 

95 

3 

2 

24 

3 

2 

62 

3 

2 

08 

3 

3 

93 

4 

3 

22 

4 

3 

61 

4 

3 

07 

4 

4 

0.9992 

0.5 

0.4 

0.9921 

5-5 

4.4 

0.9860 

10.5 

8.4 

0.9806 

15-5 

12.5 

90 

6 

4 

20 

6 

4 

59 

6 

5 

05 

6 

6 

89 

7 

5 

18 

7 

5 

58 

7 

6 

04 

7 

7 

87 

8 

6 

17 

8 

6 

56 

8 

7 

03 

8 

7 

86 

9 

7 

16 

9 

7 

55 

9 

9 

02 

9 

8 

0.9984 

I.O 

0.7 

0.9914 

6.0 

4.8 

0.9854 

II. 0 

8.8 

0.9801 

16.0 

12.9 

83 

I 

8 

13 

I 

8 

53 

I 

9 

GO 

I 

130 

81 

2 

9 

12 

2 

9 

52 

2 

90 

0.9799 

2 

I 

80 

3 

1.0 

II 

3 

5-0 

51 

3 

I 

98 

3 

2 

79 

4 

I 

09 

4 

I 

50 

4 

I 

97 

4 

2 

0.9977 

1-5 

I.I 

0.9908 

65 

5-2 

0.9849 

"•5 

9.2 

0.9796 

16.5 

13-3 

76 

6 

2 

07 

6 

2 

47 

6 

3 

95 

6 

4 

74 

7 

3 

05 

7 

3 

46 

7 

4 

94 

7 

5 

73 

8 

4 

04 

8 

4 

45 

8 

5 

92 

8 

6 

71 

9 

5 

03 

9 

5 

44 

9 

5 

91 

9 

7 

0.9970 

2.0 

1.5 

0.9902 

7.0 

5.6 

0.9843 

12.0 

9.6 

0.9790 

17.0 

13-7 

68 

I 

6 

GO 

I 

6 

42 

I 

7 

89 

I 

8 

67 

2 

7 

0.9899 

2 

7 

41 

2 

8 

88 

2 

9 

65 

3 

8 

98 

3 

8 

40 

3 

9 

87 

3 

14  0 

64 

4 

9 

97 

4 

9 

39 

4 

lO.O 

86 

4 

I 

0.9962 

2-5 

1.9 

0.9895 

7-5 

6.0 

0.9838 

12.5 

10. 0 

09785 

17  5 

14.1 

61 

6 

2.0 

94 

6 

I 

37 

6 

I 

84 

6 

2 

60 

7 

I 

93 

7 

I 

35 

7 

2 

83 

7 

3 

58 

8 

2 

92 

8 

2 

34 

8 

3 

82 

8 

4 

57 

9 

3 

90 

9 

3 

33 

9 

4 

81 

9 

5 

0.9955 

3.0 

2.3 

0.9889 

8.0 

6.4 

0.9832 

130 

10.4 

0.9780 

18.0 

145 

54 

I 

4 

88 

I 

5 

31 

I 

5 

79 

I 

6 

52 

2 

5 

87 

2 

5 

30 

2 

6 

78 

2 

7 

51 

3 

6 

86 

3 

6 

29 

3 

7 

77 

3 

8 

50 

4 

7 

84 

4 

7 

28 

4 

8 

76 

4 

9 

0.9948 

3-5 

2.8 

0.9883 

8.5 

6.8 

6.9827 

13  5 

10.9 

0-9775 

18.5 

150 

47 

6 

8 

82 

6 

9 

26 

6 

9 

74 

6 

45 

7 

9 

81 

7 

9 

25 

7 

II. 0 

73 

7 

I 

44 

8 

30 

80 

8 

7.0 

24 

8 

I 

72 

8 

2 

43 

9 

I 

78 

9 

I 

23 

9 

2 

71 

9 

3 

0.9941 

4.0 

3.2 

0.9877 

9.0 

7.2 

0.9821 

14.0 

II-3 

0.9770 

19  0 

154 

40 

I 

2 

76 

I 

3 

20 

I 

3 

69 

I 

5 

39 

2 

3 

75 

2 

3 

19 

2 

4 

68 

•     2 

5 

H 

3 

4 

74 

3 

4 

18 

3 

5 

67 

3 

6 

36 

4 

5 

73 

4 

5 

17 

4 

6 

66 

4 

7 

0.9934 

4.5 

3.6 

0.9871 

9-5 

7.6 

0.9816 

14.5 

11.7 

0.9765 

195 

15.8 

33 

6 

6 

■  70 

6 

7 

IS 

6 

8 

64 

6 

9 

32 

7 

7 

69 

7 

8 

14 

7 

8 

63 

7 

16.0 

30 

8 

8 

68 

8 

8 

13 

8 

9 

62 

8 

0 

29 

9 

9 

67 

9 

9 

12 

9 

12.0 

61 

9 

I 

WINE 


355 


S.  G. 

V. 

W. 

S.  G. 

V. 

W. 

S.  G. 

V. 

w. 

S.  G. 

V. 

w. 

0.9760 

20.0 

16.2 

0.9709' 25.0 

20.4 

0.9654 

30.0 

24.6 

0.9591 

35.0 

28.9 

59 

I 

3 

08 

I 

5 

52 

I 

7 

^9 

I 

290 

58 

2 

4 

07 

2 

6 

51 

2 

8 

88 

2 

I 

57 

3 

5 

06 

3 

6 

50 

3 

9 

86 

3 

2 

56 

4 

5 

05 

4 

7 

49 

4 

250 

85 

4 

3 

0.9755 

20.5 

16.6 

0.970425.5 

20.8 

0.9648 

30.5 

25.0 

0.958435-5 

29-3 

54 

6 

7 

03   6 

9 

461   6 

82   6 

4 

53 

7 

8 

02i    7 

21.0 

451   7 

2 

81 

7 

5 

52 

8 

9 

Oil   8 

I 

441   8 

3 

80 

8 

6 

51 

9 

,7.0 

00   9 

I 

43|   9 

4 

78 

9 

7 

0.9750 

21.0 

17.0 

0.9699  26.0 

21.2 

0.964231.0 

255 

0.957736.0 

29.8 

49 

I 

I 

981   I 

3 

40 

I 

6 

751   I 

9 

48 

2 

2 

96 

2 

4 

39 

2 

6 

74 

2 

30.0 

47 

3 

3 

95 

3 

5 

3S 

3 

7 

73 

3 

0 

46 

4 

4 

94 

4 

6 

37 

4 

8 

71 

4 

I 

0.9745 

21.5 

17.5 

0.9693  26.5 

21.6 

0.963631.5 

25.9 

0.957036.5 

30.2 

44 

6 

5 

92 

6 

7 

34 

6 

26.0 

68 

6 

3 

43 

7 

6 

91 

7 

8 

33 

7 

I 

67 

7 

4 

42 

8 

7 

90 

8 

9 

32 

8 

2 

66 

8 

5 

41 

9 

8 

89 

9 

220 

31 

9 

2 

64 

9 

6 

0.9740 

22.0 

17.9 

0.9688 

27.0 

22.1 

0.962932.0 

26.3 

09563370 

30.7 

39 

I 

18.0 

87 

I 

2 

28 

I 

4 

61 

I 

7 

38 

2 

0 

86 

2 

2 

27 

2 

5 

60 

2 

8 

37 

3 

I 

85 

3 

3 

26 

3 

6 

58 

3 

9 

36 

4 

2 

S3 

4 

4 

24 

4 

7 

57 

4 

310 

0.9735 

22.5 

18.3 

0.968227.5 

22.5 

0.9623I32.5 

26.8 

0.9556 

37.5 

31.1 

34 

6 

4 

81 

6 

6 

22 

6 

8 

54 

6 

2 

33 

7 

5 

80 

7 

7 

21 

7 

9 

53 

7 

3 

32 

8 

5 

79 

8 

7 

19 

8 

27.0 

51 

8 

4 

31 

9 

6 

78 

9 

8 

18 

9 

50 

9 

4 

0.9730 

23.0 

18.7 

0.9677 

28.0 

22.9 

0.9617 

330 

27.2 

0.954838.0 

31.5 

29 

I 

8 

76 

I 

23.0 

15 

I 

3 

47 

I 

6 

28 

2 

9 

74 

2 

I 

14 

2 

4 

45 

2 

7 

27 

3 

19.0 

73 

3 

2 

13 

3 

4 

44 

3 

8 

26 

4 

0 

72 

4 

3 

12 

4 

5 

42 

4 

9 

0.9725 

23-5 

19.1 

0.9671  28.5 

233 

0.961033.5 

27.6 

0.9541  38.5 

32.0 

24 

6 

2 

70   6 

4 

09   6 

7 

39i   6 

I 

23 

7 

3 

69   7 

5 

08 

7 

8 

38 

7 

2 

22 

8 

4 

68 

8 

6 

06 

8 

9 

36 

8 

2 

21 

9 

5 

66 

9 

7 

05 

9 

28.0 

35 

9 

3 

0.9720 

24.0 

195 

0.9665 

29.0 

23.8 

0  9604  34.0 

28.0 

0.9533390 

32.4 

19 

I 

6 

64 

I 

8 

03 

I 

I 

32 

I 

5 

18 

2 

7 

63 

2 

9 

01 

2 

2 

30 

2 

6 

17 

3 

8 

62 

3 

24.0 

GO    3 

3 

29 

3 

7 

15 

4 

9 

61 

4 

I 

0.9599   4 

4 

27 

4 

8 

9.9714 

24.5 

20.0 

0.9660  29.5 

24.2 

0.959734-5 

28.5 

0.9526  39-5 

329 

13 

6 

0 

58 

6 

3 

96 

6 

6 

24 

6 

9 

12 

7 

I 

57 

7 

4 

95 

7 

7 

23 

7 

0 

II 

8 

2 

56 

8 

4 

93 

8 

7 

21 

8 

I 

10 

9 

3 

55 

9 

5 

92 

9 

8 

20 

9 

2 

3S6 


FOOD   ANALYSIS 


S.  G. 


I 
0.9518  40.0 

16 

15 

13 

12 
0.9510 

09 

07 

05 

04 

0.9502 

01 


2 

3 

4 

40.5 

6 

7 
8 

9 
41.0 


41 


0.9499 

98 

96 
0.9494 

93 

91 

90 

88 
0.9486  42 

85 

83 

81 

80 


w. 

i 

33.3 

S.G. 

V. 

W. 

S.G. 

- 

w. 

S.G. 

V. 

1 
0.947842.5 

35-5 

0.943645.0 

37.8 

0.9391 

47-5 

4 

77 

6 

6 

34 

I 

9 

89 

6 

5 

75 

7 

7 

32 

2 

38.0 

87 

7 

6 

13 

8 

8 

31 

3 

I 

86 

8 

7 

72 

9 

9 

29 

4 

2 

84 

9 

33-7 

0.9470 

43-0 

36.0 

0.9427 

45-5 

38.3 

0.9382 

48.0 

8 

68 

I 

I 

25 

6 

3 

80 

1 

9 

67 

2 

2 

24 

7 

4 

78 

2 

340 

65 

3 

3 

22 

8 

5 

76 

3 

I 

63 

4 

3 

20 

9 

6 

74 

4 

34.2 

0.9462 

43.5 

36.4 

0.9418 

46.0 

38.7 

09373 

48.5 

3 

60 

6 

5 

17 

I 

8 

71 

6 

4 

58 

7 

6 

15 

2 

9 

69 

7 

5 

57 

8 

7 

13 

3 

390 

67 

8 

5 

55 

9 

8 

" 

4 

I 

65 

9 

34.6 

0-9453 

44  0 

36.9 

0.9409 

46.5 

39-2 

0.9363 

49  0 

7 

5' 

I 

37-0 

08 

6 

3 

61 

I 

8 

50 

2 

I 

06 

7 

3 

59 

2 

9 

48 

3 

2 

04 

8 

4 

57 

3 

35.0 

46 

4 

3 

02 

9 

5 

55 

4 

35.1 

0.9445 

44-5 

37-3 

0.9400 

470 

396 

0.9354 

49  5 

2 

43 

6 

4 

09399 

1 

7 

52 

6 

3 

41 

7 

5 

97 

2 

8 

50 

7 

4 

39 

8 

6 

95 

3 

9 

48 

8 

4 

38 

9 

7 

93 

4 

40.0 

46 

9 

w. 


40.1 

2 

3 
4 
5 
40.6 
6 

7 
8 

9 
41.0 
I 
2 
3 
4 
41-5 
6 

7 
8 

9 
41.9 
42.0 


same,  the  actual  difference  is  in  the  second  decimal  place, 
which  has  been  omitted  in  this  condensed  table. 

Alcohol  may  be  determined  by  noting  the  temperature  of 
the  vapor  from  the  boiling  liquid.  Wiley  has  described  a  form 
of  apparatus  (Fig.  53)  for  this  purpose.  It  consists  of  the  flask, 
F,  which  is  closed  by  the  rubber  stopper,  carrying  the  large 
thermometer,  B,  and  a  tube  leading  to  the  condenser,  D.  The 
vapors  which  are  given  off  during  ebullition  are  condensed  in 
D  and  return  to  the  flask  through  the  tube,  as  indicated  in  the 
figure,  entering  the  flask  below  the  surface  of  the  liquid. 

The  flask  is  heated  by  a  gas-lamp  and  is  placed  upon  a  per- 
forated disk  of  asbestos  in  such  a  way  as  to  entirely  cover  the 
hole  in  the  center  of  the  asbestos  disk,  which  is  a  little  smaller 
than  the  bottom  of  the  flask.  The  whole  apparatus  is  protected 
from  external  influences  of  temperature  by  the  glass  cylinder, 


WINE 


357 


E,  which  rests  upon  the  asbestos  disk  below  and  is  covered  with 
a  detachable,  stiff  rubber-cloth  disk  above. 

The  thermometer,  C,  indicates  the  temperature  of  the  air 
between  F  and  E.  The 
reading  of  the  thermome- 
ter, B,  should  always  be 
made  at  a  given  tempera- 
ture of  this  surrounding 
air.  The  tube  leading 
from  the  condenser,  D,  to 
the  left  is  made  long  and 
is  left  open  at  its  lower 
extremity  in  order  to 
maintain  atmospheric 
pressure  in  F  and  at  the 
same  time  prevent  the 
diffusion  of  the  alcoholic 
vapors  through  D. 

The  flame  of  the  lamp 
is  so  regulated  as  to  bring 
the  temperature  indicated 
by  the  thermometer  C  to 
about  90°  in  ten  minutes, 
for  substances  containing 
not  over  5  per  cent,  of 
alcohol.  After  boiling  for 
a  few  minutes,  the  tem- 
perature, as  indicated  in 
the  thermometer  B,  is  con- 
stant, and  the  readings  of 
the  thermometer  should  be  made  at  intervals  of  about  half  a 
minute,  for  ten  minutes.  Some  pieces  of  scrap  platinum  placed 
in  the  flask  will  prevent  bumping  and  secure  a  more  uniform 
evolution    of   vapor.    Slight  variations,   due    to    the   changes 


Fig.  53. 


358  FOOD   ANALYSIS 

in  temperature  of  the  vapors,  are  thus  reduced  to  a  minimum 
effect  upon  the  final  resuhs.  The  apparatus  is  easily  oper- 
ated, is  quickly  charged  and  discharged,  and  with  it  at  least 
three  determinations  of  alcohol  can  be  made  in  an  hour. 

The  thermometer  used  is  the  same  that  is  employed  for  the 
freezing  and  boiling  points  in  the  determination  of  molecular 
weights.  The  reading  of  the  thermometer  is  arbitrary,  but 
the  degrees  indicated  are  centigrade.  The  thermometer  is  set 
in  the  first  place  by  putting  the  bulb  in  water  containing  16 
grams  of  common  salt  to  100  c.c;  when  the  water  is  fully 
boiling,  the  excess  of  mercury  is  removed  from  the  column  in 
the  receptacle  at  the  top,  and  then,  on  placing  in  boiling  water, 
the  column  of  mercury  will  be  found  a  little  above  the  5°  mark. 
This  will  allow  a  variation  in  all  of  5°  in  the  temperature,  and 
a  thermometer  thus  set  can  be  used  for  the  estimation  of  per- 
centages of  alcohol  from  one  to  five  and  a  half,  by  volume. 
When  the  liquor  contains  a  larger  percentage  of  alcohol  than 
this,  it  is  advisable  to  dilute  it  until  it  reaches  the  limit. 

In  order  to  avoid  frequent  checking  of  the  thermometer, 
rendered  necessary  by  changes  in  barometric  pressure,  a  second 
apparatus,  made  exactly  like  the  one  described,  is  used,  in 
which  water  is  kept  constantly  boiling.  It  is  only  necessary, 
in  this  case,  to  read  the  two  thermometers  at  the  same  instant, 
in  order  to  make  the  necessary  correction  required  by  changes 
in  barometric  pressure. 

Each  0.8°  corresponds  to  about  i  per  cent,  by  volume  of 
alcohol  in  liquors  containing  not  more  than  5.5  per  cent.  For 
example,  if,  in  a  given  case,  the  temperature  of  the  vapor  of 
boiling  water,  as  marked  by  the  thermometer,  is  5.155°  and 
the  temperature  of  that  from  a  sample  of  beer  is  2.345°,  the 
difference  is  equivalent  to  2.810°,  and  the  percentage  of  alcohol 
by  volume  is,  therefore,  2.81  divided  by  0.80  =  3.51. 

The  thermometer  used  is  graduated  to  hundredths  of  a 
degree,  and  may  be  read  by  a  cathetometer  to  0.005°.     I^  ^^^7 


WINE  359 

be  protected  and  its  readings  facilitated  by  immersing  the  bulb  in 
a  test-tube  containing  water. 

Extract  is  determined  as  indicated  on  page  27.  When  the 
amount  exceeds  6  per  cent.,  it  will  be  best  to  dilute  the  sample 
with  an  equal  volume  of  water,  making  allowance  for  this  in 
calculating  resuhs.  Some  operators  advise  the  use  of  50  c.c. 
for  this  determination,  but  good  results  can  be  obtained  in 
small  dishes  with  5  c.c. 

Ash. — The  residue  from  the  extract  determination  is  incin- 
erated at  as  low  a  heat  as  possible.  Repeated  moistening, 
drying,  and  heating  to  redness  are  advisable  to  get  rid  of 
carbon. 

Gum  and  Dextrin  (in  wine). — 4  c.c.  of  the  sample  are  mixed 
with  10  c.c.  of  96  per  cent,  alcohol.  If  gum  arabic  or  dextrin 
is  present,  a  lumpy,  thick,  and  stringy  precipitate  is  produced; 
pure  wine  becomes  at  first  opalescent  and  then  gives  a  flocculent 
precipitate. 

Total  Acidity. — Any  carbonic  acid  present  is  removed  by 
shaking  a  portion  of  the  sample;  25  c.c.  are  transferred  to  a 
beaker  and,  with  white  wines,  10  drops  of  azolitmin  solution 
added.  Decinormal  sodium  hydroxid  solution  is  added  until 
the  red  color  changes  to  blue.  The  result  is  expressed  in  terms 
of  tartaric  acid,  i  c.c.  of  ^^  alkali  equals  0.0075  gram  tartaric 
acid. 

Determination  oj  Volatile  Acids. — 50  c.c.  of  wine  to  which  a 
little  tannin  has  been  added,  to  prevent  foaming,  are  distilled 
in  a  current  of  steam.  The  flask  is  heated  until  the  liquid 
boils,  the  lamp  turned  down,  and  the  steam  passed  through 
until  200  c.c.  have  been  collected  in  the  receiver.  The  dis- 
tillate is  titrated  with  ^^  sodium  hydroxid  solution,  and  the 
result  expressed  as  acetic  acid:  i  c.c.  -^  sodium  hydroxid 
solution  equals  0.006  gram  acetic  acid. 

Total  Sulfites. — 25   c.c.  of  normal  potassium  hydroxid  are 


360  FOOD   ANALYSIS. 

placed  in  a  200  c.c.  flask,  50  c.c.  of  the  sample  added,  best 
by  means  of  a  pipet,  the  liquids  mixed  and  allowed  to  stand 
15  minutes  with  occasional  shaking.  10  c.c.  of  dilute  (25 
per  cent),  sulfuric  acid  are  added,  with  3  c.c.  of  starch  solution, 
and  the  mixture  titrated  with  -^  iodin  solution  introduced  as 
rapidly  as  possible.  The  number  of  c.c.  of  iodin  required  to 
secure  a  blue  color  lasting  for  some  minutes,  multiplied  by 
0.00128,  will  give  the  equivalent  of  sulfur  dioxid  in  grams  per 
100  c.c. 

Sulfurous  Acid. — 50  c.c.  of  the  sample  are  mixed  in  a  200  c.c. 
flask  with  5  c.c.  of  dilute  sulfuric  acid  (i  :  3),  a  small  piece  of 
sodium  carbonate  added  to  expel  air  and  the  solution  titrated 
with  ^  iodin  solution  as  directed  above.     The  c.c.  of  solution 

so 

required  multiplied  by  0.00128  gives  the  weight  of  sulfur  dioxid 
in  grams  per  100  c.c.  of  sample. 

A  sample  of  Bordeaux  wine,  examined  in  1904  by  the  U.  S. 
Customs  authorities,  was  refused  admission  on  the  ground  of 
excessive  content  of  sulfur  dioxid  and  sulfites.  The  sample 
gave  the  following  results,  which  accord  closely  with  those 
reported  by  the  official  analyst. 

Total  sulfur  dioxid, 0.070  per  100  c.c. 

Sulfurous  acid  (calculated  as  sulfur  dioxid), 0.045  " 

Glycerol. — loo  c.c.  of  wine  are  evaporated  in  a  porcelain 
dish  to  about  lo  c.c,  i  gram  of  quartz  sand  and  2  grams  of 
milk  of  lime  containing  40  per  cent,  calcium  hydroxid  added, 
and  the  evaporation  cautiously  carried  almost  to  dryness.  The 
residue  is  mixed  with  50  c.c.  of  alcohol,  90  per  cent,  by  weight, 
using  a  glass  pestle  or  spatula  to  break  up  any  solid  particles, 
heated  just  to  boiling  on  the  water-bath,  allowed-  to  settle, 
and  the  liquid  filtered  into  a  flask  graduated  at  100  and  no  c.c. 
The  residue  is  repeatedly  extracted  in  a  similar  manner  with 
10  c.c.  portions  of  hot  alcohol.  The  contents  of  the  flask  are 
cooled  to  15°,  diluted  with  alcohol  to  the  100  c.c.  mark,  and 


WINE  361 

filtered  rapidly.  50  c.c.  of  the  filtrate  are  evaporated  to  a  sirup 
in  a  porcelain  dish  on  hot,  but  not  boiling  water,  the  residue 
transferred  to  a  small  glass- stoppered  graduated  cylinder, 
with  the  aid  of  20  c.c.  absolute  alcohol,  and  three  portions  of 
20  c.c.  of  pure  ether  added,  shaking  well  between  each  addition. 
The  mixture  is  allowed  to  stand  until  clear,  decanted  through 
a  filter,  the  cylinder  washed  at  least  three  times  with  a  mix- 
ture of  I  part  absolute  alcohol  and  1.5  parts  of  pure  ether, 
the  washings  being  added  to  the  filtrate.  The  latter  is  evapo- 
rated to  a  sirup,  dried  for  one  hour  at  100°,  and  weighed.  The 
weight  doubled  gives  the  grams  of  glycerol  per  100  c.c.  of  sample. 

Added  Colors:  see  pages  64  to  75. 

Saccharin. — A  substance  capable  of  simulating  a  saccharin 
reaction  by  the  method  given  on  page  81  often  occurs  in  wine. 
The  elimination  of  the  fallacy  has  been  specially  studied  by 
Chace,^"  who  suggests  the  following  method: 

50  c.c.  of  the  sample  are  extracted  with  ether  in  the  usual 
way,  the  residue  dissolved  in  water  and  extracted  with  pe- 
troleum spirit.  This  is  evaporated,  a  small  portion  tested  for 
salicylic  acid,  and  then,  whether  found  or  not,  the  remainder 
of  the  residue  is  returned  to  the  liquid  from  which  it  was  ex- 
tracted. The  mixture  is  made  up  to  10  c.c,  i  c.c.  of  dilute  sul- 
furic acid  (i  :  3)  and  an  excess  of  5  per  cent,  solution  of  po- 
tassium permanganate  added,  and  the  liquid  brought  to  boiling. 
If  salicylic  acid  was  shown  in  the  test  of  the  petroleum  spirit 
extraction,  the  solution  is  boiled  for  one  minute;  but  if  not,  this 
length  of  boiling  is  unnecessary.  While  the  solution  is  still  hot, 
a  small  piece  of  sodium  hydroxid  is  added  (sufficient  to  render 
the  liquid  alkaline),  and  after  a  few  minutes  the  iron  and  man- 
ganese hydroxids  are  filtered  off,  the  liquid  evaporated  to  dry- 
ness in  a  silver  or  nickel  dish,  and  heated  to  2io°-2i5°  for  20 
minutes.  The  residue  is  dissolved  in  water,  acidified  with  dilute 
sulfuric  acid,  extracted  with  ether  or  other  suitable  solvent  and 
tested  for  salicylic  acid.  If  the  reaction  occurs,  saccharin  was 
present  in  the  sample. 
32 


362  FOOD   ANALYSIS 

Salicylic  Acid.  The  tannin  in  many  articles  may  mask 
or  simulate  faint  reactions  for  salicylic  acid  with  ferric  salts. 
Alcohol  also  may  interfere.  Harry  &  Mummery^ ^  recommend 
a  method  for  avoiding  this:  100  c.c.  of  the  sample  are  rendered 
faintly  alkahne  with  sodium  hydro xid,  and  concentrated  at 
a  temperature  just  below  the  boiling,  until  most  of  the  alcohol 
is  removed.  The  liquid  is  made  up  to  nearly  the  original 
volume  and  placed  in  a  flask  marked  at  300  c.c,  20  c.c.  of 
a  saturated  solution  of  lead  subacetate  are  added,  and  the 
solution  made  alkaline  by  25  c.c.  of  normal  sodium  hydroxid. 
Tannins  are  thrown  down;  lead  salicylate  passes  into  the 
alkahne  solution.  Some  albuminous  and  pectinous  bodies 
may  also  be  dissolved;  these  are  reprecipitated  by  adding 
20  c.c.  of  normal  hydrochloric  acid  solution.  The  mass  is 
made  up  to  the  mark  with  water,  shaken,  filtered  through  a 
dry  filter,  200  c.c.  of  the  filtrate  collected  and  acidified  dis- 
tinctly, but  not  excessively,  with  hydrochloric  acid.  The 
Hquid  is  refiltered,  if  necessary,  and  extracted  with  the  immis- 
cible solvent  as  usual. 

The  method  is  applicable  to  many  articles.  Among  other 
advantages  it  prevents  the  formation  of  an  emulsion  with  the 
immiscible  solvent.  For  semisohd  materials  such  as  jams 
and  jelhes  50  grams  should  be  crushed  and  mixed  with  a  Httle 
water  before  adding  the  lead  solution. 

Harry  &  Mummery  use  three  successive  extractions  with 
ether,  and  then  make  a  quantitative  analysis  by  evaporating 
the  ether,  dissolving  the  residue  in  dilute  alcohol,  making  up 
to  100  c.c.  and  comparing  the  color  produced  with  ferric  chlorid 
with  that  produced  by  a  similar  solution  of  known  strength. 

Caramel  and  Prune  Juice. — An  extraction  method  for  de- 
tecting these  spirits  has  been  devised  by  Crampton  &  Simons": 

50  c.c.  of  the  sample  are  evaporated  on  the  water-bath  nearly 
to  dryness,  the  residue  washed  into  a  50  c.c.  flask,  25  c.c.  of 
absolute  alcohol  added,  and  the  solution,  after  cooling  to  stan- 


WINE  363 

dard  temperature,  made  up  to  the  50  c.c.  mark  and  mixed.  25 
c.c.  are  transferred  to  a  separating  apparatus  and  agitated  with 
50  c.c.  of  ether  at  intervals  for  about  thirty  minutes.  When  the 
layers  are  separated,  the  water  layer  is  diluted  to  25  c.c,  the 
contents  of  the  flask  are  shaken,  and  the  liquids  again  allowed 
to  separate.  The  water-layer  will  be  increased  slightly,  and 
25  c.c.  of  it  should  be  drawn  off  for  comparison  with  the 
25  c.c.  of  solution  which  has  not  been  treated  with 
ether.  By  comparing  the  two  liquids  in  a  tinto- 
meter, quantitative  observations  may  be  made.  The 
coloring- matter  of  oak-wood  is  soluble  in  ether, 
and,  therefore,  spirits  not  artificially  colored  become 
lighter  when  treated  by  this  method.  (See  also 
page  125.) 

Crampton  &  Simons  advise  the  use  of  Bramwell's 
modification  of  Rose's  apparatus  for  the  operation. 
It  is  shown  in  figure  54.  The  upper  bulb  should 
have  a  capacity  of  about  150  c.c;  the  lower  bulb 
should  have  a  capacity  of  25  c.c,  including  a  por- 
tion of  the  connecting  stem.  This  stem  should  have 
a  caliber  about  4  mm.  and  it  is  graduated  in  0.02 
c.c.  from  20  c.c  to  25  c.c,  the  upper  mark  only 
being  shown  in  the  figure.  For  diluting  the  watery 
layer  as  directed  in  the  process,  it  is  best  to  attach  a 
rubber  tube  to  the  lower  opening  and  connect  the 
other  end  of  the  rubber  tube  to  a  flask  of  water.  By 
elevating  the  flask  and  controlling  the  flow  of  water  by  Fig.  54. 
the  stopcock,  any  amount  of  liquid  may  be  introduced. 

Fusel  Oil. — Of  the  many  processes  devised  for  this  deter- 
mination, the  following  is  selected.  It  is  transcribed  as  given 
in  the  Bulletin  of  the  A.  O.  A.  C.  The  separator  (Fig.  54)  is 
used;    the  reagents  are: 

Alcohol  free  from  jusel  oil  prepared  by  fractional  distillation 
over  sodium  hydroxid  and  diluted  so  as  to  contain  exactly 


364  FOOD  ANALYSIS 

30  per  cent,  of  absolute  alcohol  by  volume  (sp.  gr.,  0.96541 
at  15.6°). 

Anhydrous  chlorojorm  redistilled. 

Diluted  sulfuric  acid  (sp.  gr.,  1.2857  at  15.6°). 

Analytic  operation:  200  c.c.  of  the  sample  are  distilled 
until  about  25  are  left,  the  flask  is  allowed  to  cool,  25  c.c.  of 
water  added  to  the  contents,  and  distilled  again  until  the  total 
distillate  measures  200  c.c.  The  volume-percentage  of  this  is 
ascertained  and  it  is  diluted  to  30  per  cent,  by  the  rule  given 
below. 

To  dilute  any  sample  of  alcohol  to  a  given  percentage  mix 
a  volumes  of  the  alcohol  with  sufficient  water  to  make  b  vol- 
umes of  the  product,  a  being  the  volume-percentage  desired 
and  b  the  volume-percentage  of  the  original  liquid.  Allow 
the  mixture  to  stand  until  full  contraction  has  occurred  and 
the  original  temperature  has  been  reached  and  make  up  any 
deficiency  with  water.  For  example,  to  dilute  a  distillate 
containing  50  per  cent,  of  alcohol  by  volume  until  it  contains 
30  per  cent.,  30  volumes  of  the  50  per  cent,  alcohol  are  mixed 
with  enough  water  to  make  50  volumes. 

The  special  tube  and  separate  flasks  containing  sufficient  of 
the  various  reagents  and  the  properly  diluted  distillate  are  im- 
mersed in  water  at  15°  until  all  have  attained  that  temperature. 
The  tube  should  have  a  rubber  cap  over  the  lower  end  to  pre- 
vent entrance  of  water.  When  the  temperature  is  reached, 
the  tube  is  filled  to  the  20  c.c.  mark  with  chloroform,  drawing 
it  through  the  lower  end  by  suction;  then  100  c.c.  of  the  purified 
alcohol  are  added  and  i  c.c.  of  the  diluted  sulfuric  acid,  the 
apparatus  inverted,  and  shaken  vigorously  for  3  minutes.  The 
stopcock  should  be  opened  a  couple  of  times  to  equalize  pres- 
sure. The  tube  is  placed  for  15  minutes  in  water  at  15°,  turn- 
ing occasionally  to  hasten  the  separation  of  the  reagents,  and 
then  the  volume  of  the  chloroform  noted.  After  thoroughly 
cleansing  and  drying  the  apparatus,  the  operation  is  repeated, 


WINE  365 

using  the  diluted  distillate  from  the  sample  under  examination, 
in  place  of  the  purified  alcohol.  The  increase  in  the  chloroform 
volume  with  the  sample  under  examination  over  that  with  the 
standard  alcohol  is  due  to  fusel  oil,  and  this  difference  (expressed 
in  c.c),  multiplied  by  0.663,  gives  the  volume  of  fusel  oil  in 
100  c.c,  which  is  equal  to  the  percentage  of  fusel  oil  by  volume 
in  the  30  per  cent,  distillate.  This  must  be  calculated  to  the 
percentage  of  fusel  oil  by  volume  in  the  original  liquor. 

Gallisin  and  Foreign  Bitters. — For  the  detection  of  gallisin, 
indicating  the  use  of  commercial  glucose,  the  following  method, 
due  to  Haarstick,'^  is  recommended:  i  liter  of  the  beer  is 
evaporated  to  a  thin  sirup,  and  300  c.c.  of  90  per  cent,  alco- 
hol gradually  added  in  quantities  of  i  to  2  c.c,  and  finally  95 
per  cent,  alcohol  until  the  filtrate  does  not  give  the  slightest 
turbidity  on  further  addition  of  the  latter.  The  liquid  is  filtered 
after  standing  for  twelve  hours,  most  of  the  alcohol  distilled 
off,  and  the  remainder  evaporated.  The  residue  is  dissolved 
in  water,  diluted  to  1000  c.c,  and  fermented  at  20°  with  well- 
washed  beer  yeast.  After  two  or  three  days  a  little  fresh  yeast 
is  added,  and  on  the  fourth  day  fermentation  is  complete. 
The  concentrated  liquor  will  show  no  dextrorotation  if  no  gal- 
lisin was  present. 

The  outline  process,  given  on  page  366,  for  the  detection 
of  foreign  bitter  principles  in  beer  is  due  to  AUen^* : 

Methyl  Alcohol. — Crude  methyl  alcohol  is  sometimes  added 
to  ethyl  alcohol  to  unfit  the  latter  for  use  as  a  beverage.  The 
invention  of  methods  by  which  methyl  alcohol  can  be  rectified 
so  as  to  have  but  slight  odor,  has  led  to  the  adulteration  of 
alcohohc  beverages  and  medicines  by  it.  For  this,  Milliken  & 
Scudder^^  devised  the  following  test: 

If  the  sample  be  a  concentrated  spirit,  it  should  be  diluted 
three  or  four  times  before  taking  a  portion  for  test.  When 
various  organic  bodies  are  present,  as  in  malt  liquors  and 
tinctures,  the  sample  should  be  distilled  and  the  portion  pass- 


366 


FOOD  ANALYSIS 


looo  c.c.  are  evaporated  half  and  precipitated  boiling  with  lead  acetate,  the  liquid  boiled 
for  fifteen  minutes  and  filtered  hot.  If  any  precipitate  occur  on  cooling,  the  liquid  is 
again  filtered. 


Filtrate.  The  excess  of  lead  is  removed  by  hydrogen  sulfid,  and  the 
filtered  liquid  concentrated  to  about  150  c.c.  and  tasted.  If  bitter,  the 
liquid  is  slightly  acidulated  with  dilute  sulfuric  acid,  and  shaken  re- 
peatedly with  chloroform. 


Precipitate 
contains  hop- 
bitter,  c ar a- 
niel-  bitter, 
ophelic  acid 
(from       chir- 

etta),  Phos-  Chloroform  layer,  on 
phates,  albu-  evaporation,  leaves  a  bit- 
mmous  mat-  ^gr  extract  in  the  case  of 
ters,  etc.  gentian,    calumba,    quas- 

sia, and  old  hops  (only 
slightly  or  doubtfully  bit- 
ter in  the  case  of  chiretta).  The  residue  is 
dissolved  in  a  little  alcohol,  hot  water 
added,  and  the  hot  solution  treated  with 
ammoniacal  basic  lead  acetate  and  filtered. 


Precipitate  contains  old 
hops,  gentian,  and  tiaces 
of  caraw^/ products.  It  is 
suspended  in  water,  de- 
composed by  hydrogen 
sulfid,  and  the  snhition 
agitated  with  chloroform. 


Chloroform 
LAYER  is  ex- 
amined by 
special  tests 
for  gentian 
and  old  tiop- 
bitter. 


Aqueous 
liquid 
contains 
traces  of 
caramel- 
bitter. 


Filtrate  is 
boiled  to  re- 
move ammo- 
nia, and 
treated  with 
a  slight  ex- 
cess of  sul- 
furic acid,  fil- 
tered and 
tasted.  I f 
bitter,  it  is 
agitated 
with  chloro- 
form, and 
the  residue 
examined 
for  calumba 
and  quassia. 


Aqueous  liquid  is  shaken  with  ether. 


Ethereal  layer  leaves 
a  bitter  residue  in  the 
case  of  chiretta,  gen- 
tian, or  calumba.  It  is 
dissolved  in  a  little  al- 
cohol, hot  water  added, 
and  the  hot  solution 
treated  with  ammoni- 
acal basic  lead  acetate 
and  filtered. 


P  r  E  C  I  P  I- 

Filtrate 

tate     is 

is  treated 

treated 

with        a 

with 

slight  ex- 

water 

cessof  di- 

and    de- 

lute    sul- 

composed 

furic 

by  hydro- 

acid,   fil- 

gen    sul- 

tered and 

fid.     The 

tasted. 

filtered 

Bitter- 

liquid    is 

ness  indi- 

bitter   in 

cates  cal- 

presence 

umba    or 

of     gen- 

■    chiretta, 

tian. 

which 

may       be 

re-ex- 

tracted 

with  ether 

and      fur- 

ther    ex- 

amined. 

Aqueous  li- 

QUID,      if 
still  bitter 
is  rendered 
alkaline 
and 
shaken 
with  ether- 
c  hi oro- 
form.        A 
bitter     ex- 
tract    may 
be    due   to 
berberin 
(calumba) 
or    strych- 
nin. 


The  aqueous 
liquid, 
separated 
from       the 
ether-chlo- 
reform, 
may  con- 
tain cara- 
mel-bitter 
or  cholin. 


ing  over  between  50°  and  100°  collected.  This  distillate 
should  give  a  clear  colorless  solution  when  shaken  with  water. 
In  some  cases,  as  when  acids  or  phenoHc  bodies  are  present, 
it  will  be  advisable  to  add  sodium  hydroxid  before  distilling. 
A  convenient  amount  of  the  material  to  be  tested  is  placed  in 
a  beaker  which  is  set  in  a  dish  of  cold  water. 

A  close  spiral  of  about   2   cm.   long  is  made  by  winding 
copper  wire  around  a  lead-pencil.     The  metal  is  superficially 


WINE  367 

oxidized  by  heating  in  the  upper  part  of  the  Bunsen  flame,  and 
while  red-hot  plunged  into  the  distilled  or  diluted  sample, 
as  noted  above.  This  treatment  is  repeated  at  least  six 
times,  rinsing  the  wire  in  cold  water  between  each  heating. 
The  liquid  is  then  tested  by  either  the  phloroglucol  or  phe- 
nylhydrazin  test,  as  given  on  page  83.  The  method  will 
detect  at  least  one  per  cent,  of  methyl  alcohol.  If  much  ethyl 
aldehyde  be  present  in  the  liquid,  it  will  be  of  advantage  to 
boil  the  liquid,  after  the  hot  wire  treatment,  in  a  flask  attached 
to  an  inverted  condenser,  as  ethyl  aldehyde  evaporates  more 
readily  under  these  conditions  than  formaldehyde. 

It  is  necessary  to  prove  the  absence  of  formaldehyde  before 
making  the  test.  This  can  generally  be  done  best  by  the 
phenylhydrazin  test.  If  formaldehyde  is  present  it  can  be 
wholly  removed  by  adding  a  moderate  excess  of  potassium 
cyanid,  and  distilling.  The  distilled  liquid  will  contain  no 
formaldehyde  if  the  cyanid  had  been  added  in  sufficient  amount. 
As  the  amount  of  formaldehyde  in  foods,  beverages  and  tinc- 
tures is  small,  it  will  usually  be  found  that  i  c.c.  of  a  normal 
solution  of  potassium  cyanid  will  be  ample  for  the  purpose. 
After  adding  the  potassium  cyanid,  a  portion  of  the  liquid  may  be 
at  once  tested  with  phenylhydrazin;  if  no  bluish  or  greenish 
color  is  produced,  the  remaining  portion  of  the  liquid  should 
be  at  once  distilled.  A  small  portion  of  the  distillate  should, 
as  a  precaution,  be  tested  for  formaldehyde. 

Borates,  present  in  many  pulp  fruits,  can  be  detected  by 
evaporating  about  20  grams  of  the  juice  or  fruit  to  dryness, 
burning  off  and  treating  the  ash  by  the  turmeric  test.  (See 
page  82.)  A  proportion  of  borates,  equivalent  to  i  part  of 
boric  acid  to  5000  parts  of  wine,  can  be  detected  by  the  flame 
test.  50  c.c.  of  the  sample  are  neutralized  with  sodium 
hydroxid,  evaporated  to  dryness,  charred  and  the  carbon  bum 
off  somewhat.  The  residue  is  cooled,  mixed  with  a  little 
sulfuric  acid  and  2  c.c.  of  alcohol  and  lighted.     In  a  darkened 


368  FOOD   ANALYSIS 

place,  the  boric  acid  flame  is  easily  seen.  It  may  be  verified 
by  the  spectroscope. 

The  quantitative  determination  of  borates  in  fruit  or  juices, 
fermented  or  unfermented,  may  be  satisfactorily  carried  out 
by  the  method  of  Allen  &  Tankard.'' 

100  c.c.  of  the  hquid  is  evaporated  to  dryness  with  10  c.c.  of  a 
10  per  cent,  solution  of  calcium  chlorid.  In  the  case  of  solid  or 
semisolid  materials,  the  mass  should  be  well  broken  up  and  the 
solution  of  calcium  chlorid  well  mixed  with  it.  The  dry  mass 
is  well  charred,  boiled  with  150  c.c.  of  water,  and  the  liquid 
filtered.  The  residue  is  ashed  thoroughly,  boiled  with  a 
second  portion  of  150  c.c.  of  water,  allowed  to  stand  for  12 
hours,  and  filtered  cold.  The  filtrates  are  mixed,  evaporated 
to  30  c.c,  cooled  and  neutrahzed  with  ^  acid  and  methyl 
orange.  An  equal  volume  of  glycerol  and  a  little  phenol- 
phthalein  solution  are  added  and  the  liquid  titrated 
with  ~  sodium  hydroxid  (free  from  carbonate).  10  c.c. 
more  of  glycerol  should  be  added.  If  the  titration  is  complete, 
the  red  will  remain,  i  c.c.  of  the  sodium  hydroxid  solution 
represents  0.00175  boric  anhydrid,  equivalent  to  0.0031 
orthoboric  acid. 

Care  must  be  taken  that  all  the  boric  acid  is  in  solution  be- 
fore beginning  the  titration.  Allen  &  Tankard  recommend 
that  the  residue  be  extracted  with  a  third  portion  of  150  c.c.  and 
this  titrated  separately.  It  should  give  no  boric  anhydrid; 
if  it  does,  the  amount  can  be  added  to  the  other  result. 

The  process  depending  on  the  volatihty  of  methyl  borate 
is  more  troublesome  and  not  more  accurate. 

Bigelow  has  described  the  following  approximation  method 
for  borates:  A  series  of  solutions  containing  amount's  of  boric 
acid  from  o.ooi  to  0.020  gram  in  dilute  hydrochloric  acid  (i  part 
of  strong  acid  to  15  parts  of  water)  is  prepared.  A  drop  of 
each  solution  is  evaporated  on  a  piece  of  turmeric  paper  2  cm. 


WINE  369 

square  and  the  color  noted,  care  being  taken  that  the  drops 
are  uniform.  50  c.c.  of  the  wine  are  made  slightly  alkaline 
with  calcium  hydroxid  solution,  evaporated  to  dryness,  and 
burned  to  an  ash.  3  c.c.  of  water  are  added  to  the  ash  and 
then  half- strength  hydrochloric  acid  drop  by  drop  until  the 
liquid  is  acid.  The  solution  is  then  made  up  to  5  c.c.  with 
hydrochloric  acid  one- sixth  the  strength  of  the  strong  acid, 
the  mass  mixed,  and  a  drop  tested  on  a  piece  of  turmeric  paper 
and  compared  with  the  standards.  If  stronger  than  a  standard 
that  is  of  characteristic  tint,  the  liquid  should  be  diluted  with 
I  to  15  hydrochloric  acid  and  again  tested. 

Sucrol  (Dulcin)  (Jorisson's  method  as  given  by  A.  O. 
A.  C). — 100  c.c.  of  the  sample,  if  liquid,  or  a  corresponding 
amount  of  solid  or  semisolid  material,  are  mixed  with  5  grams 
of  lead  carbonate,  evaporated  to  sirupy  consistence  and  ex- 
tracted several  times  with  90  per  cent,  alcohol.  The  alcohol 
is  evaporated  to  dryness,  the  residue  extracted  with  ether  and 
the  ether  allowed  to  evaporate  without  heat.  The  residue 
thus  obtained  is  stirred  up  with  5  c.c.  of  water,  mixed  with 
3  c.c.  of  a  10  per  cent,  solution  of  mercuric  nitrate  and  heated 
for  10  minutes  on  the  water-bath.  A  violet-bluish  tint  is 
produced  if  dulcin  is  present.  The  tint  is  changed  to  deep 
violet  by  addition  of  lead  dioxid. 

Polarimetric  Examination. — In  the  routine  examination  of 
wine  polarimetric  readings  are  taken  directly  (after  clarifica- 
tion, if  necessary).  Sweet  wines  are  examined  directly,  also 
after  inversion  and  fermentation.  The  following  are  the  direc- 
tions for  these  processes  given  by  the  A.  O.  A.  C. : 

Clarification. — For  white  wines,  60  c.c.  of  the  sample  are 
mixed  with  3  c.c.  of  lead  subacetate  solution  and  3  c.c.  of  water 
and  filtered.  (The  method  of  clarification  by  powdered  lead 
subacetate,  with  removal  of  the  lead  by  potassium  oxalate  as 
described  on  page  118,  might  be  advantageous.)  2>?)  c-^-  ^^ 
the  filtrate  are  mixed  with  1.5  c.c.  of  a  saturated  solution  of 


37©  FOOD   ANALYSIS 

sodium  carbonate  and  1.5  c.c.  of  water,  again  filtered,  and  ex- 
amined in  the  polarimeter.  The  reading  must  be  multipHed 
by  1.2  to  compensate  for  the  dilution.  For  red  wines  the  same 
amount  of  sample  is  taken,  and  6  c.c.  of  lead  subacetate  solution 
are  used  without  addition  of  water.  33  c.c.  of  the  filtrate  are 
treated  with  3  c.c.  saturated  sodium  carbonate  solution,  filtered, 
and  the  reading  multiplied  by  1.2.  With  sweet  wines  100  c.c.  are 
mixed  with  2  c.c.  of  lead  subacetate  solution  and  8  c.c.  of  water 
and  filtered.  55  c.c.  of  the  filtrate  are  mixed  with  0.5  c.c.  of 
saturated  sodium  carbonate  solution  and  4.5  c.c.  of  water, 
filtered,  and  the  reading  multiplied  by  1.2;  33  c.c.  of  the  filtrate, 
prior  to  the  addition  of  the  sodium  carbonate,  are  mixed  with 
3  c.c.  of  hydrochloric  acid  and  the  liquid  inverted  according  to 
the  method  on  page  119.  The  liquid  is  cooled  quickly,  filtered, 
the  reading  taken  at  known  temperature,  and  multiplied  by 
1.2.  50  c.c.  of  the  sample  are  freed  from  alcohol  by  concen- 
tration, made  up  to  the  original  volume  with  water,  mixed  with 
some  well-washed  beer  yeast,  and  the  mass  kept  at  30°  until 
fermentation  is  complete,  which  will  usually  require  from  48  to 
72  hours.  The  liquid  is  then  transferred  to  a  100  c.c.  flask,  a 
few  drops  of  acid  mercuric  nitrate  added  (p.  213),  then  some 
lead  subacetate  solution,  followed  by  the  saturated  sodium 
carbonate  solution.  The  flask  is  filled  to  the  mark,  the  liquid 
mixed,  filtered,  and  the  reading  multiplied  by  2. 

The  polarimetric  data  obtained  in  the  above  examinations 
are  interpreted  according  to  the  following  schedule: 

If  the  direct  examination  shows  no  rotation,  the  sample  may 
nevertheless  contain  invert-sugar  associated  with  the  dextro- 
rotatory unfermentable  impurities  of  glucose  or  with  sucrose. 
If  inversion  results  in  a  levorotation,  sucrose  was  present.  If 
fermentation  results  in  dextrorotation,  it  shows  that  invert - 
sugar  (or  some  other  levorotatory  fermentable  carbohydrate) 
and  the  unfermentable  constituents  of  glucose  were  present. 
If  the  inversion  or  fermentation  produces  no  change,  sucrose, 


MALT-EXTRACTS  371 

unfermentable  constituents  of  glucose,  and  levorotatory  sugars 
are  absent. 

If  the  direct  examination  shows  dextrorotation,  sucrose  and 
the  unfermentable  constituents  of  glucose  may  be  present. 
If  after  inversion  it  is  levorotatory,  sucrose  was  present;  if 
dextrorotatory  to  more  than  2.3  divisions  of  the  sugar  scale, 
the  unfermentable  impurities  of  glucose  were  present;  if  the 
dextrorotation  is  less  than  2.3  divisions  and  more  than  0.9,  a 
portion  of  the  original  specimen  must  be  submitted  to  the 
following  treatment:  21b  c.c.  are  mixed  with  i.i  gram  of 
potassium  acetate  and  evaporated  to  a  thin  sirup,  which  is 
mixed  with  200  c.c.  of  90  per  cent,  alcohol,  with  constant 
stirring,  the  solution  is  filtered,  the  alcohol  removed  by  distil- 
lation until  about  5  c.c.  remain,  the  residue  is  mixed  with  washed 
bone-black,  filtered  into  a  graduated  cylinder,  and  washed 
until  the  filtrate  amounts -to  30  c.c.  If  this  filtrate  shows  a 
dextrorotation  of  more  than  1.5  divisions  on  the  sugar  scale, 
the  impurities  of  glucose  were  present. 

If  the  direct  examination  shows  levorotation,  and  this  is 
increased  by  inversion,  sucrose  and  levorotatory  sugar  were 
present.  If  the  sample  after  fermentation  shows  levorotation 
of  3  divisions,  it  contains  only  levorotatory  sugars.  If  after 
fermentation  it  rotates  to  the  right,  levorotatory  sugars  and 
the  unfermentable  impurities  of  glucose  were  present. 

MALT-EXTRACTS 

Some  commercial  malt-extracts  are  semi-solid  mixtures  of 
diastase  with  products  of  hydrolysis  of  starch,  such  as,  maltose, 
dextrose,  and  dextrin.  No  alcohol  is  present;  preservatives 
and  coloring-matters  are  not  likely  to  be  used.  Other  extracts 
are  dark- colored  liquids,  containing  from  3  to  7  per  cent,  of 
alcohol,  5  to  15  per  cent,  of  solids,  mostly  organic,  but  little, 
if  any,  active  diastase.  Preservatives  are  liable  to  be  used  in 
this  class,  salicylic  acid  being  the  most  common. 


372  FOOD  ANALYSIS 

The  usual  examination  of  malt-extracts  will  involve  detec- 
tion of  preservatives,  determination  of  alcohol,  solid  matter, 
and  diastatic  power.  Qualitative  tests  for  diastase  may  be 
made  as  follows:  50  c.c.  of  a  solution  of  5  grams  arrow- 
root starch  in  1000  c.c.  of  water,  made  as  directed  below,  are 
mixed  with  about  i  gram  of  the  extract  to  be  tested,  and  the 
mixture  heated  in  a  water-bath  within  the  limits  of  35°  and  45°. 
Every  few  minutes  a  drop  of  the  liquid  is  tested  on  a  porcelain 
plate  with  a  drop  of  iodin  solution  (page  26),  until  the  blue  color 
ceases  to  appear.  It  is  not  worth  while  to  continue  the  ex- 
periment beyond  a  half  hour,  as  a  malt-extract  that  will  not 
transform  the  starch  in  that  time  is  of  no  diastatic  value.  The 
solution  should  not  be  acid.  For  quantitative  measurement, 
it  is  necessary  to  determine  the  reducing  sugar  formed  in  presence 
of  a  large  amount  of  starch.  10  grams  of  arrowroot  starch  are 
stirred  into  about  100  c.c.  of  cold  water,  the  mixture  added,  with 
constant  stirring,  to  250  c.c.  of  boihng  water,  and  the  boihng 
continued  until  the  starch  is  well  diffused  through  the  mass. 
The  solution  is  diluted  to  500  c.c.  when  cold.  50  c.c.  of  this 
solution  are  mixed  with  0.5  gram  of  the  sample  and  the  mix- 
ture kept  at  a  temperature  between  35°  and  45°  for  half  an 
hour.  The  reducing  sugar  is  measured  by  the  volumetric 
method  described  on  page  113,  care  being  taken  that  the  liquid 
is  sufficiently  diluted.  An  experiment  without  addition  of 
starch  must  be  made  to  determine  the  amount  of  reducing 
substance  in  the  extract. 

In  some  cases  rough  comparative  approximations  may  be 
made  by  comparing  the  color  produced  by  iodin  at  the  end  of 
the  heating,  but  the  liquid  must  be  largely  diluted,  and  the 
indications  are  merely  suggestive. 

Alcohol  and  solids  are  determined  as  in  alcoholic  beverages. 


FLESH-FOODS  373 

FLESH-FOODS 
Descriptions  of  anatomic  and  histologic  characters  of  flesh- 
foods  need  not  be  given  here.  The  following  table,  from  data 
compiled  by  Allen,  will  show  the  principal  constituents  of  some 
meats.  The  figures  are  percentages;  they  must  be  regarded 
as  approximations,  as  the  analytic  processes  are  imperfect. 
The  proteid  was  obtained  probably  by  multiplying  the  total 
nitrogen — found  by  the  Kjeldahl  method — by  6.25  or  approxi- 
mate factor. 

Meat  from:  Water. 

Ox  (lean), 76.7 

Ox  (fat), 55.4 

Mutton, 76.0 

Mutton  (fat), 48.0 

Pig, 72.6 

Horse, 74.3 

Hare, 74.1 

Deer, 75.7 

Chicken, 76.2 

Pigeon, 75.1 

Lobster, 76.6 

Oyster, 80.3 

Herring, 74.6 

Mackerel, 71.2 

Salmon, 64.3 

Cod, 82.2 

Grindley^^  has  investigated  the  action  of  pure  water  at  a  tem- 
perature not  over  10°  on  raw  and  cooked  beef.  Some  of  his 
results  are  given  in  the  annexed  table.  The  nitrogenous  com- 
pounds are  in  all  cases  obtained  by  multiplying  the  Kjeldahl 
nitrogen  by  6.25. 

Cold  Water  Extract  of 
Raw.  Boiled.        Raw  Beef.  Boiled  Beef. 


*OTEID. 

Fat. 

Ash. 

20.7 

1-5 

1.2 

17.1 

26.3 

I.I 

I7.I 

S-7 

1-3 

14.8 

36.4 

0.8 

19.9 

6.2 

I.I 

21.6 

2-5 

1.0 

23-3 

I.I 

I.I 

19.7 

1.9 

I.I 

19.7 

1.4 

1-3 

22.1 

I.O 

1.0 

I9.I 

I.I 

I.I 

I4.I 

1-5 

2.7 

14-5 

9.0 

1-7 

19.4 

8.0 

1-3 

21.6 

12.7 

1-3 

16.2 

0.3 

1-3 

Total  proteids, 19.96  37 

Coagulable  proteids, 

Albumoses, 

Peptones, 

Meat-bases, 

Acid,  (calculated  as  lactic), . . . 
Ash, 


70 


2.18 

0.05 

0.08 

0.12 

0.03 

O.IO 

1.05 

0.87 

1.09 

1. 14 

I.I4 

0.85 

374  FOOD  ANALYSIS 

The  higher  proteid  content  of  boiled  beef  was  due  largely 
to  the  lower  proportion  of  water. 

Grindley  found  that  after  extraction  of  raw  meat  with  pure, 
cold  water,  a  lo  per  cent,  solution  of  sodium  chlorid  will  ex- 
tract much  additional  matter,  largely  coagulable  proteids. 
Very  little  proteid  matter  is  extracted  from  boiled  beef  by  pure 
water  or  sodium  chlorid  solution. 

Adulteration. — Meats  are  not  adulterated  in  the  sense  in 
which  that  word  is  commonly  used,  but  cheap  meats  are  sub- 
stituted for  dear  {e.  g.,  horse  meat  in  sausages  and  mince- 
meat), the  meat  of  diseased  and  immature  animals  is  often 
sold,  preservatives  are  employed,  and  appHcations  made  to 
improve  color  or  texture.  The  detection  of  entozoa  is  a  matter 
of  importance.  Tests  for  incipient  and  actual  decomposition 
may  be  required. 

Analytic  Methods. 

Water. — 5  grams  of  the  finely  divided  material  are  dried 
according  to  the  methods  described  on  pages  27-32,  Parson's 
method  being  especially  worth  trial  in  this  connection. 

Ash. — The  dry  residue  obtained  in  the  water  determina- 
tion is  incinerated  according  to  the  methods  given  on  pages 
39  to  41. 

Total  Nitrogen. — The  Kjeldahl- Gunning  process  is  em- 
ployed. The  nitrogen,  mulitplied  by  6.25,  will  give  an  ap- 
proximation to  the  proteids  present.  If  nitrates  are  present, 
as  will  be  the  case  with  some  preserved  meats,  the  modified 
process,  page  37,  must  be  used. 

Fat. — Much  of  the  fat  in  meat  samples  can  be  removed  by 
mechanical  methods,  but  some  adheres  obstinately  to  the 
muscle-tissue,  and  it  is  probable  that  errors  have  beeii  made 
in  this  respect,  as  with  condensed  milk.  It  has  been  suggested 
that  the  muscle-tissue  be  digested  with  pepsin  and  hydro- 
chloric acid  and  the  fat  extracted  from  the  mass.  Good  re- 
sults have  been  claimed  for  the  following  process:  2  grams 


FLESH- FOODS  375 

of  the  material  are  shaken  frequently  for  six  hours  with  200 
c.c.  of  ether  and  2  c.c.  of  mercury  and  the  fat  determined  in 
an  aliquot  part  of  the  mixture. 

Most  investigators  use  too  much  material.  It  is  probable 
that  results  near  enough  for  practical  purposes  could  be  ob- 
tained by  continuous  extraction  for  some  hours  of  a  few  grams 
of  the  material,  but  care  should  be  taken  that  the  sample  rep- 
resents a  fair  average  of  the  specimen  and  that  it  is  very  finely 
divided  without  loss  of  fat.  If  the  fat  is  to  be  examined,  a 
large  amount  of  it  should  be  extracted  by  mechanical  means, 
and  not  with  solvents,  unless  there  are  special  reasons  to  the 
contrary. 

Horseflesh. — The  detection  of  horseflesh  is  difficult.  Many 
processes  have  been  proposed,  but  they  are  all  open  to  objec- 
tion. The  principal  reliance  is  upon  the  detection  of  glycogen, 
which  is  present  in  horseflesh  in  much  greater  proportion  than 
in  most  other  flesh. 

A  brief  qualitative  method  may  be  used  for  glycogen  (Cour- 
ley  &  Coremons^*) : 

50  grams  of  the  material  are  boiled  for  30  minutes  with  water, 
strained,  and  a  portion  of  the  filtrate  mixed  with  a  few  drops 
of  potassium  iodid-iodin  solution  (page  26).  With  a  large 
percentage  of  horse-meat,  the  glycogen  will  produce  a  dark 
brown  liquid,  destroyed  by  heating  and  reappearing  on  cooling. 
If  starch  is  present,  it  must  be  removed,  by  adding  to  a  portion 
of  the  filtrate  2  volumes  of  glacial  acetic  acid,  again  filtering 
and  testing  this  filtrate  as  above.  The  following  quantitative 
method  (Pflueger  &  Nerking^")  is  provisionally  recommended 
by  A.  O.  A.  C. 

50  grams  of  the  finely-macerated  meat  are  digested  on  the 
water-bath  with  200  c.c.  of  2  per  cent,  solution  of  potassium 
hydroxid,  until  solution  is  practically  complete.  The  liquid 
is  cooled,  diluted  to  20  c.c.  with  water,  shaken,  filtered  through 
a  dry  filter,  and  100  c.c.  of  the  filtrate  mixed  with  10  grams  of 


376  FOOD  ANALYSIS 

potassium  iodid  and  i  gram  of  potassium  hydroxid,  which 
are  stirred  in  until  dissolved.  50  c.c.  of  alcohol  are  added  and 
the  mixture  allowed  to  stand  overnight.  The  glycogen  will 
separate.  It  is  collected  by  filtration,  washed  with  a  solution 
containing  i  c.c.  of  a  73  per  cent,  solution  of  potassium  hy- 
droxid, 10  grams  of  potassium  iodid,  100  c.c.  of  water  and  50 
c.c.  of  alcohol.  The  material  is  then  washed  with  a  mixture 
of  2  volumes  of  alcohol  and  i  of  water,  containing  sodium  chlorid 
in  the  proportion  of  0.007  gram  per  liter,  the  residue  dissolved 
in  water  the  remaining  proteids  removed  by  solution  of  potas- 
sium mercuric  iodid.  Filter  if  necessary,  add  sodium  chlorid  in 
the  proportion  0.002  gram  per  100  c.c,  precipitate  the  glycogen 
again  by  the  alcohol-sodium  chlorid  solution  noted  above,  wash 
with  alcohol  containing  0.007  gram  sodium  chlorid  per  liter, 
then  with  absolute  alcohol,  finally  with  ether,  dry  to  constant 
weight  and  weigh. 

As  control,  the  glycogen  may  be  hydrolyzed  by  boiling  for 
3  hours  with  hydrochloric  acid  diluted  with  10  parts  of  water, 
and  the  reducing  sugar  determined  as  on  page  113,  multiplying 
the  result  by  0.9  for  glycogen. 

Bremer  states  that  the  most  definite  test  for  horseflesh  is 
the  character  of  the  intramuscular  fat.  For  this  test,  all  visible 
fat  is  removed  from  a  sample,  the  mass  finely  minced,  and  heated 
in  water  for  an  hour  at  100°.  The  fat  that  floats  is  poured 
off  with  the  water,  the  flesh  washed  several  times  with  boiling 
water,  dried  for  twelve  hours  at  100°,  and  the  material  then 
extracted  for  several  hours  with  petroleum  spirit  of  low  boiling- 
point.  Part  of  the  fat  thus  obtained  may  be  set  aside  for  the 
determination  of  iodin  number,  but  most  of  it  should  be  sa- 
ponified, the  excess  of  alkali  carefully  neutralized  with  acetic 
acid,  and  any  alcohol  that  may  have  been  used  in  the  saponifi- 
cation removed  by  evaporation  on  the  water-bath.  The  glyc- 
erol-soda  method  would  seem  to  be  applicable  here.  The 
soap  is  dissolved  in  water,  a  hot  solution  of  zinc  acetate  added 


FLESH-FOODS  377 

in  the  proportion  of  i  part  of  the  salt  to  2  of  fat,  the  precipitate 
washed  with  hot  water  and  alcohol,  pressed  between  folds  of 
filter-paper,  and  heated  with  ten  times  its  volume  of  anhydrous 
ether  for  thirty  minutes  under  a  reflux  condenser.  The  solu- 
tion is  cooled,  filtered  into  a  separating  funnel,  mixed  with 
dilute  hydrochloric  acid,  the  ethereal  layer,  which  contains 
the  acids,  washed  with  water,  and  parts  of  it  filtered  into  weighed 
flasks,  the  ether  evaporated,  and  the  iodin  number  determined. 

It  is  stated  that  horseflesh  always  gives  a  reddish-brown 
tint  to  the  petroleum  spirit  solution,  but  bull's  flesh  also  gives 
such  a  tint.  If,  however,  glycogen  has  been  detected  by  the 
tests  already  mentioned,  the  petroleum  spirit  solution  is  reddish- 
brown,  the  iodin  number  of  the  fat  exceeds  65  and  that  of  the 
liquid  acids,  obtained  as  above,  is  considerably  over  95,  the 
presence  of  horseflesh  may  be  inferred. 

Starch  is  often  added  in  large  amount  to  sausage,  deviled 
meats  and  similar  articles.  It  may  be  detected  as  noted  on  page 
87,  but  it  must  be  remembered  that  it  may  be  used  in  small 
amount  to  facilitate  mixture,  and  may  occur  in  spices,  and  in 
some  brands  of  table-salt.  A  slight  reaction  should  be  dis- 
regarded. 

The  determination  of  starch  cannot  be  carried  out  by  the 
standard  reduction  methods  on  account  of  interference  of  some 
of  the  meat-constituents.  For  approximation  the  method  of 
Ambiihl,  with  slight  modification,  is  suggested  by  A.  O.  A.  C.*" 

2  grams  of  the  sample  are  thoroughly  macerated  with  100 
c.c.  of  water,  then  boiled  for  30  minutes  and  the  liquid  made 
up  to  200  c.c,  mixed,  filtered,  an  aliquot  portion  taken,  tested 
with  the  potassium  iodid-iodin  solution  (page  26)  and  the 
color  compared  with  a  solution  containing  a  known  amount  of 
the  same  kind  of  starch  as  that  in  sample.  The  last  point  may 
be  determined  by  microscopic  examination. 

Coloring-matter. — Meats  are  not  infrequently  colored  to 
give  them  a  fresh  look  or  to  improve  naturally  pale  samples. 


378  FOOD  ANALYSIS 

Sausage  meats  are  often  colored.  Carmine  and  coal-tar  colors, 
especially  the  latter,  are  often  employed.  Fuchsin  and  eosin 
are  among  these,  but  Allen  states  that  benzopurpurin  is  the 
most  common.  The  detection  of  artificial  colors  will  generally 
be  acomplished  satisfactorily  by  the  test  on  page  64.  E.  Spath 
has  found  that  heating  the  material  for  a  short  time  on  the 
water-bath  with  a  5  per  cent,  solution  of  sodium  salicylate  will 
often  dissolve  out  colors  not  otherwise  soluble.  Ordinarily, 
water  or  alcohol  will  take  out  sufficient  for  the  wool-test.  For 
the  detection  of  carmine,  the  method  of  Klinger  and  Bujard, 
modified  by  Bremer,  may  be  used :  20  grams  of  the  minced  mate- 
rial are  heated  for  several  hours  with  a  mixture  of  equal  parts 
of  glycerol  and  water  slightly  acidulated  with  tartacic  acid.  The 
yellow  liquid  is  freed  from  fat,  filtered,  and  the  coloring-matter 
precipitated  as  a  lake  by  the  addition  of  alum  and  ammonium 
hydroxid.  This  is  washed,  dissolved  in  a  little  tartaric  acid, 
and  examined  in  the  spectroscope.  Absorption  bands  lying 
between  the  position  of  b  and  D  of  the  solar  spectrum  are 
characteristic  of  carmine. 

Improvers  and  Preservatives. — Mixtures  of  potassium  ni- 
trate, sodium  chlorid,  and  other  mineral  preservatives  with  a 
little  coloring-matter — the  latter  almost  always  a  coal-tar  color — 
are  sold  for  improving  the  appearance  of  meat.  Sulfites  are 
also  used  as  improvers — acid  sodium  sulfite  being  a  common 
form — in  quantity  equivalent  to  0.5  to  i  per  cent,  calculated 
as  sulfur  dioxid.  Salicylic  acid  and  borates  are  also  used.  As 
these  are  all  soluble  in  cold  water,  they  may  be  extracted  by 
simple  maceration,  the  watery  solution  being  concentrated  at 
a  low  temperature  and  treated  as  directed  on  pages  78  to  85. 
Formaldehyde  is  not  likely  to  be  used  in  meat  on  account  of 
its  hardening  action  on  proteids. 

Chace  ^^  found  aluminum  oxyacetate  (basic  acetate)  as 
a  preservative  in  canned  sausage  in  amounts  yielding  from 
1 1.2  to  31.3  of  aluminum  oxid  to  100  grams  of  material.     The 


FLESH- FOODS  379 

qualitative  test  is  made  as  follows:  25  grams  of  the  material 
are  partially  ashed  in  a  platinum  vessel,  exhausted  with  hy- 
drochloric acid,  sodium  hydroxid  added  in  excess,  the  liquid 
boiled,  filtered,  the  filtrate  acidified  with  hydrochloric  acid, 
and  ammonium  hydroxid  added.  Aluminum  hydroxid  and 
aluminum  phosphate  are  thrown  down.  Aluminum  is  not 
a  constituent  of  normal  flesh  in  appreciable  amount.  For 
quantitative  methods,  the  process  of  Fresenius  &  Wacken- 
roder  is  used.     (See  page  386.) 

Putrejaction. — To  detect  incipient  putrefaction,  Ebers  pro- 
posed the  following  test:  A  rod  moistened  with  a  mixture  of 
hydrochloric  acid  i  c.c,  alcohol  3  c.c,  and  ether  i  c.c.  is  held 
over  the  suspected  material.  The  formation  of  fumes  of  am- 
monium chlorid  shows  that  putrefaction  has  begun.  Care 
must  be  taken  not  to  mistake  the  fumes  of  the  hydrochloric 
acid  for  those  of  ammonium  chlorid. 

Nitrates. — These  are  generally  in  the  form  of  added  potas- 
sium nitrate  and  may  be  determined  by  the  following  method, 
which  so  far  as  the  preparation  of  the  sample  is  concerned  is 
due  to  Given.^^  The  operation  must  be  preceded  by  a  deter- 
mination of  the  chlorids  present,  as  these  interfere  with  the 
process.  This  can  easily  be  done  by  titrating  in  the  usual 
manner  a  cold  water  solution  of  the  finely  divided  meat,  i 
gram  in  200  c.c.  will  be  convenient 

For  nitrates,  i  gram  of  the  sample  is  placed  in  a  100  c.c. 
flask,  50  c.c.  of  water  added,  and  the  mixture  kept  in  hot  water 
for  20  minutes,  with  occasional  shaking.  For  each  i  per  cent, 
of  sodium  chlorid  present,  3  c.c.  of  a  saturated  solution  of 
silver  sulfate  are  added,  then  10  c.c.  of  lead  subacetate  and  5 
c.c.  of  alumina-cream,  shaking  after  each  addition.  The  liquid 
is  made  up  to  100  c.c,  shaken,  filtered  through  a  plaited,  dry, 
filter,  the  filtrate  being  returned  until  it  is  clear.  20  c.c.  of  the  fil- 
trate are  evaporated  on  the  water-bath  in  a  shallow  porcelain 
dish  to  dryness  and  mixed  with  i  c.c.  of  the  phenoldisulfonic 


380  FOOD   ANALYSIS 

acid  described  below,  the  acid  being  stirred  over  the  whole  dish 
with  a  glass  rod  so  as  to  touch  all  parts  of  the  residue.  Heat 
is  not  needed.  The  liquid  is  diluted  with  water,  rinsed  into  a 
nesslerizing  glass,  the  dish  rinsed  several  times,  these  rinsings 
being  added  to  the  first,  and  then  ammonium  hydroxid  or 
sodium  hydroxid  is  added  to  distinct  alkaline  reaction. 

The  nitrates  form  picric  acid,  the  alkali  forms  a  picrate; 
the  depth  of  color  of  this  is  proportional  to  the  amount  present. 
The  determination  is  made  by  comparing  the  color  with  that 
produced  by  a  solution  of  potassium  nitrate  of  known  strength 
treated  in  the  same  manner,  that  is,  evaporation  on  water-bath, 
admixture  with  i  c.c.  of  the  phenoldisulfonic  acid,  and  addition 
of  alkali. 

The  phenoldisulphonic  acid  is  prepared  as  follows:  37 
grams  of  pure  sulfuric  acid  and  3  grams  of  pure  phenol  are 
heated  for  six  hours  in  a  flask  immersed  in  boiling  water.  The 
reagent  may  crystalhze  on  cooling,  but  can  be  easily  liquefied 
by  gentle  warming. 

The  nitrate  solution  for  comparison  may  be  made  by  dis- 
solving o.ioo  gram  of  pure  dry  potassium  nitrate  in  water  to 
make  100  c.c.  i  c.c.  of  this  is  evaporated  in  a  porcelain  dish 
on  the  water  bath,  the  residue  mixed  with  i  c.c.  of  phenol- 
disulfonic acid,  stirred,  diluted  with  water  and  rendered  alkaline 
as  noted  above.  The  solution  is  diluted  to  the  same  volume 
as  that  of  the  solution  from  the  meat  and  the  colors  compared. 

The  nitrate  indicated  in  the  solution  of  the  sample  is  one- 
fifth  of  that  present,  since  20  c.c.  out  of  the  100  c.c.  are  taken. 
The  standard  nitrate  solution  is  such  that  i  c.c.  contains  o.ooi 
gram  of  potassium  nitrate.  If  the  two  solutions  are  of  equal 
tint,  0.005  gram  of  potassium  nitrate  was  in  the  sample,  i.  ^.,  o.  5 
per  cent. 

If  the  two  solutions  are  very  different  in  depth  of  color,  evapo- 
ration of  a  second  portion  of  standard  nitrate  solution  must  be 
made,  taking,  as  far  as  can  be  judged,  enough,  more  or  less, 


FLESH- FOODS  38 1 

to  approximate  closely  to  the  other  solution.  When  the  depth 
of  color  is  not  widely  different  in  the  two  solutions,  they  can  be 
compared  by  pouring  out  the  deeper  solution  until,  when  placing 
the  glasses  side  by  side  upon  a  pure  white  surface  and  looking 
down  through  the  hquids,  the  tints  are  sensibly  equal.  The 
relative  volumes  of  the  liquid  will  then  be  a  basis  for  calcula- 
tion.    For  example: 

I  gram  of  sample  treated  as  directed  is  made  up  to  50  c.c, 
which  volume  contains  the  picrate  equivalent  of  the  nitrate 
in  0.2  gram  of  the  sample;  if,  now,  i  c.c.  of  standard  nitrate 
also  treated  and  made  up  to  50  c.c.  gives  a  liquid  which  is  the  same 
depth  of  color  as  25  c.c.  of  the  liquid  from  the  sample,  then: 

50  c.c.  from  standard  =  o.ooi  potassium  nitrate. 
25  c.c.  from  sample  =  o.ooi  potassium  nitrate. 
50  c.c.  from  sample  =  0.002  potassium  nitrate. 
0.002  X  5  =  o.oio  potassium  nitrate  =  i  per  cent. 

Injected  Meats. — The  lower  animals  are  subject  to  para- 
sitic diseases  communicable  to  human  beings.  The  most 
important  are  two  species  of  so-called  tapeworm  and  the 
Trichina  spiralis.  One  species  of  tapeworm,  Tcenia  saginata, 
is  found  in  one  stage  of  development  in  beef;  another  species, 
T.  solium^  is  found  in  pork.  This  condition  is  often  termed 
"measles."  Trichina  spiralis  is  principally  found  in  pork. 
Many  other  animal  parasites  are  known,  but  recognition  of 
them  belongs  to  pathology  and  biology. 

Tcenia  saginata  Goeze,  also  called  T.  mediocannellata,  occurs 
in  beef  as  little  white  cysts  among  the  muscular  fibers,  Hke 
knots  in  wood.  The  mature  animal  is  developed  from  the 
cysts  when  the  meat  is  eaten.  It  is  the  common  tapeworm 
of  the  United  States. 

Tcenia  solium  L.  occurs  in  the  flesh  of  the  hog. 

Trichina  spiralis  Owen  is  a  worm  that  occurs  in  hog-flesh 
as  light-colored  cysts,  smaller  than  a  pin's  head,  and  usually 


382  FOOD  ANALYSIS 

lying  with  the  long  diameter  in  the  direction  of  the  muscular 
fiber.  The  cysts  contain  immature  worms,  which  are  released 
when  the  cyst  is  digested;  the  worm  quickly  reaches  matur- 
ity, multipHes  rapidly,  and  distributes  itself  through  various 
tissues  of  the  host. 

The  detection  of  the  various  parasites  of  meat  can  often  be 
attained  by  examining  with  a  good  hand-glass.  With  higher 
powers,  the  organism  can  be  seen  in  more  detail. 

Canned  Meats. — These  are  now  usually  prepared  on  a 
very  large  scale  at  estabhshments  under  inspection  and  hence 
are  but  little  liable  to  adulteration.  Preservatives,  except 
common  salt  and  niter,  are  not  likely  to  be  employed.  If  any 
other  preservative  should  be  used  it  will  probably  be  boric  acid 
or  possibly  salicylic  acid,  either  of  which  can  be  easily  detected 
in  the  extract  with  cold  water  by  methods  given  elsewhere. 
Tin  and  sometimes  lead  are  absorbed  in  small  amounts  from 
the  can  or  solder.  These  may  be  tested  for  by  the  methods 
given  on  page  58.  Examination  under  moderate  magnifying 
power  will  detect  parasitic  infection.    (See  pages  378  and  386.) 

Meat-extracts. — These  are  now  offered  in  great  variety. 
Some  contain  partly  digested  proteids  (proteoses  and  peptones), 
but  in  many  samples  the  most  abundant  nitrogenous  ingredients 
are  the  so-called  meat-has es^  a  class  of  amido-derivatives  of  which 
kreatin,  kreatinin,  and  xanthin  are  examples.  Many  pro- 
prietary articles,  intended  especially  for  invalid  feeding,  con- 
tain much  alcohol  and  carbohydrates  (maltose,  lactose,  dex- 
trine).    Some  contain  notable  amounts  of  iron  and  manganese. 

Many  investigations  of  these  preparations  have  been  made, 
but  the  processes  of  analysis  are  still  in  dispute  and  the  results 
obtained  by  different  observers  do  not  agree.  The  following 
methods  are  compiled  from  the  work  of  Allen,  Mitchell  and 
Grindley. 

Water ^  Ash,  and  Total  Nitrogen  are  determined  as  indicated 
under  those  titles  in  the  introductory  part. 


FLESH-FOODS  383 

Fat  is  usually  present  in  but  small  amount,  and  is  extracted 
more  accurately  by  petroleum  spirit  or  carbon  tetrachlorid  than 
by  ether,  applying  the  methods  described  on  pages  41  to  43. 

Insoluble  matter,  which  may  include  some  meat-fiber,  is  de- 
termined by  treating  from  5  to  25  grams  (depending  on  whether 
the  preparation  is  sohd  or  liquid)  with  cold  water,  filtering,  and 
drying  the  residue  at  100°.  A  microscopic  examination  of  this 
should  be  made. 

Proteids,  Peptones,  and  Meat-bases.  The  following  method 
has  been  suggested  by  Allen, *^  partly  from  his  own  experiments 
and  partly  from  those  of  Bomer: 

50  c.c.  of  a  solution  of  a  known  weight  of  the  sample,  of 
such  strength  as  to  contain  about  1.5  grams  of  nitrogenous 
bodies,  are  freed  from  insoluble  material,  mixed  with  i  c.c.  of 
diluted  sulfuric  acid  (i  to  4),  and  saturated  with  zinc  sulfate 
by  stirring  in  the  powdered  salt  until  no  more  dissolves.  Zinc 
sulfate  containing  the  full  amount  of  water  of  crystallization 
disssolves  in  about  half  its  weight  of  water  at  room  tempera- 
ture, but  the  commercial  salt  is  usually  partly  effloresced,  and 
will  often  cake  when  added  to  the  solution.  When  the  liquid 
is  saturated  with  zinc  sulfate,  the  precipitate  is  assumed  to 
contain  all  the  albumin  and  gelatin  and  immediate  derivatives 
(proteoses),  but  no  peptone.  It  is  separated  by  filtration, 
washed  with  a  saturated  solution  of  zinc  sulfate,  and  the  filter 
and  precipitate  treated  by  the  Kjeldahl- Gunning  method.  The 
nitrogen  obtained,  multiplied  by  6.25,  will  give  approximately 
the  amount  of  nitrogenous  bodies  precipitated. 

The  filtrate  and  washings  are  made  up  to  200  c.c,  mixed, 
and  100  c.c.  transferred  to  a  flask  of  the  larger  form  described 
on  page  33,  enough  hydrochloric  acid  added  to  make  the  liquid 
strongly  acid  to  litmus,  and  then  bromin  water  by  moderate 
portions,  with  active  shaking  or  stirring,  until  there  is  an 
excess  of  bromin  present.  The  precipitate  may  be  flocculent 
at  first,  but  most  of  it  soon  becomes  viscous  and  adherent.     It 


384  FOOD   ANALYSIS 

is  allowed  to  stand  until  the  free  portions  have  settled,  when 
it  is  decanted  through  an  asbestos  filter  either  in  a  Gooch  cru- 
cible or  in  an  apparatus  similar  to  that  described  on  page  115. 
The  precipitate  is  washed  several  times  with  cold  water  con- 
taining some  hydrochloric  acid  and  bromin,  but  it  is  advisable 
to  keep  the  washings  at  first  separate  from  the  main  filtrate. 
The  contents  of  the  filter-tube  are  returned  to  the  vessel  in 
which  the  precipitation  was  made,  10  c.c.  of  sulfuric  acid 
added,  and  the  mass  cautiously  treated  until  it  chars  and  vapors 
of  bromin  are  evolved,  after  which  10  grams  of  potassium  sul- 
fate are  added  and  the  operation  conducted  as  described  on  pages 
33  to  37.  The  nitrogen,  multiplied  by  6.33,  will  give  ap- 
proximately the  peptone. 

The  process  of  A.  O.  A.  C.  suggests  liquid  bromin  (2  c.c.) 
instead  of  bromin  water. 

By  deducting  from  the  total  nitrogen  the  sum  of  the  nitro- 
gen figures  obtained  from  the  zinc  sulfate  and  bromin  precipi- 
tates, and  multiplying  the  remainder  by  3.12,  an  approxima- 
tion to  the  meat-bases  will  be  obtained.  These  meat-bases 
are  in  the  filtrate  from  the  bromin  precipitate,  but  the  bromin, 
hydrochloric  acid,  and  zinc  sulfate  will  be  likely  to  interfere 
with  the  determination  of  the  nitrogen.  The  zinc  sulfate, can 
be  removed  by  cautious  addition  of  either  potassium  carbon- 
ate or  barium  hydroxid,  but  the  bromin  will  be  apt  to  form 
hypobromites,  which  will  decompose  some  of  the  meat  bases 
with  evolution  of  nitrogen. 

A  more  satisfactory  plan  seems  to  be  that  outlined  by  Bau- 
mann  and  Bomer:  The  remaining  portion,  100  c.c,  from  the 
zinc  sulfate  precipitate  is  mixed  with  excess  of  sodium  phos- 
phomolybdate  (see  page  274),  by  which  the  meat^bases,  pep- 
tones, and  ammonium  compounds  are  precipitated.  This 
precipitate  is  removed  by  filtration  under  pressure,  so  as  to  draw 
out  as  much  as  possible  of  the  mother  liquor,  and  the  nitrogen 
determined   as  usual.     The   nitrogen   due   to  peptone   being 


FLESH- FOODS  385 

known,  that  due  to  meat-bases  and  ammonium  compounds 
can  be  calculated.  To  determine  the  ammonium  compounds, 
a  known  weight  of  the  original  sample  should  be  distilled  with 
barium  carbonate,  the  distillate  being  collected  in  a  known 
quantity  of  standard  acid,  which  is  afterward  titrated. 

Meat-extracts  may  contain  coagulable  proteids.  These  may 
be  estimated  by  rendering  the  filtrate  solution  distinctly  acid 
with  acetic  acid  and  boiling  for  five  minutes.  The  coagulum 
may  be  weighed  directly  or  the  nitrogen  in  it  estimated  by  the 
Kjeldahl-Gunning  method  and  multiplied  by  6.25  for  proteid. 

As  solutions  of  proteids,  proteoses,  and  peptones  are  strongly 
levorotatory,  while  most  of  the  meat-bases  that  occur  in  these 
extracts  are  inactive,  some  information  might  be  gained  by  con- 
centrating the  liquid  from  the  zinc  sulfate  precipitate  and  ex- 
amining it  in  the  polarimeter,  filtering  if  necessary.  A  solution 
that  has  no  appreciable  optic  activity  will  not  be  likely  to 
contain  much  peptone.  Another  special  test  that  may  be  ap- 
plied to  this  liquid  is  the  so-called  biuret  reaction.  Bomer  ap- 
plies this  as  follows:  The  filtrate  from  the  zinc  sulfate  pre- 
cipitation is  decolorized  by  shaking  with  animal  charcoal  and 
the  zinc  sulfate  decomposed  by  excess  of  sodium  carbonate  or 
cautious  addition  of  barium  hydroxid.  The  filtered  solution  is 
rendered  alkaline  with  sodium  hydroxid  and  a  drop  or  two  of 
very  dilute  solution  of  copper  sulfate  added.  Peptones  give 
a  rose-red  tint. 

Preservatives  may  be  added  to  meat-extracts,  although  this 
is  not  usual.  Boric  acid  will  be  most  likely  to  be  used,  and 
the  methods  on  page  367  will  suffice  for  its  detection.  Poi- 
sonous metals  are  not  likely  to  be  present,  but  may  be  sought 
for,  if  deemed  necessary,  by  the  methods  given  on  pages  57 
to  64.  Some  preparations  may  require  examinations  for  iron 
and  manganese.  These  will  be  obtained  in  solution  by  heating 
the  ash  in  strong  hydrochloric  acid,  and  may  be  separated  and 
determined  by  the  standard  methods  of  mineral  analysis. 

34 


386  FOOD   ANALYSIS 

Addendum  to  page  378. — Fresenius  &  Wackenroder's 
process  for  the  determination  of  aluminum,  as  described  by 
Chace'^: 

A  weighed  amount  of  the  finely  comminuted  sausage  is 
heated  over  a  low  flame  until  danger  of  spurting  is  past. 
(The  low-temperature  burner,  page  52,  figure  31,  will  be  sat- 
isfactory.) The  mass  is  then  heated  until  thoroughly  charred, 
cooled  and  digested  for  some  time  on  the  water-bath  with 
hydrochloric  acid,  filtered,  slightly  washed,  and  the  filter  and 
residue  ashed.  This  ash  should  be  gray  and  small  in  amount; 
it  is  dissolved  in  hydrochloric  acid,  the  solution  filtered  and 
the  filtrate  added  to  the  other  solution.  Any  appreciable 
residue  on  the  filter  should  be  tested  for  aluminum.  The 
combined  filtrates  are  made  slightly  alkaline  by  ammonium 
hydroxid,  and  barium  chlorid  added  until  no  further  precipi- 
tate is  formed.  This  consists  of  barium  phosphate,  aluminum 
hydroxid  and  aluminum  phosphate.  It  is  washed,  and  dis- 
solved in  the  least  possible  amount  of  hydrochloric  acid. 
This  solution  is  saturated  with  barium  carbonate.  Potassium 
hydroxid  is  added  in  excess  and  the  mass  digested  for  some 
time;  then  sodium  carbonate  is  added,  the  barium  carbonate 
and  phosphate  separated  by  filtration  and  thoroughly  washed. 

The  filtrate  is  acidulated  with  hydrochloric  acid,  and  the 
aluminum  determined  in  the  usual  way. 


SPECIFIC   GRAVITY   OF   WATER. 


387 


SPECIFIC  GRAVITY  OF 
Water  at  0°  =  0.99987 


WATER  FROM 
Water  at  4°  - 


0°  TO  icxj° 
=  1. 00000 


I 

0.99992 

26 

0.99686 

51 

0.9S772 

76 

0.97438 

2 

96 

27 

60 

52 

25 

77 

0.97377 

3 

99 

28 

33 

53 

0.98677 

78 

16 

4 

1 .00000 

29 

05 

54 

29 

79 

0.97255 

5 

0.99999 

30 

0.99576 

55 

0.98581 

80 

0.97194 

6 

97 

31 

77 

56 

34 

81 

32 

7 

93 

32 

47 

57 

0.98486 

82 

0.97070 

8 

88 

33 

0.99485 

58 

37 

83 

07 

9 

82 

34 

■ 
52 

59 

0.98388 

84 

0.96943 

ID 

74 

35 

18 

60 

38 

85 

0.96879 

II 

65 

36 

0.99383 

61 

0.98286 

86 

15 

12 

54 

37 

47 

62 

34 

87 

0.96751 

13 

43 

38 

10 

63 

0.98182 

88 

0.96687 

14 

29 

39 

0.99273 

64 

28 

89 

22 

15 

16 

40 

35 

65 

0.98074 

90 

0.96556 

16 

00 

41 

0.99197 

66 

19 

91 

0.96490 

17 

0.99884 

42 

58 

67 

0.97964 

92 

23 

18 

65 

43 

18 

68 

08 

93 

0.96356 

19 

46 

44 

0.99078 

69 

0.97851 

94 

0.96288 

20 

25 

45 

37 

70 

0.97794 

95 

19 

21 

04 

46 

0.98996 

71 

36 

96 

0.96149 

22 

0.99782 

47 

54 

72 

0.97677 

97 

0.96079 

23 

60 

48 

10 

73 

18 

98 

08 

24 

36 

49 

0.98865 

74 

0.97558 

90 

0.95937 

25 

12 

50 

19 

75 

0.97498 

100 

0.95866 

388 

FOOD   ANALYSIS 

Correspondence  of 

Centigrade  and  Fahrenheit  Degrees 

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

20 

392.0 

393-8 

395-6 

397.4 

399-2 

401.0 

402.8 

404.6 

406.4 

408.2 

19 

374-0 

375-8 

377-6 

379-4 

381.2 

3830 

384.8 

386.6 

388.4 

390.2 

18 

356.0 

357.8 

359.6 

361.4 

363-2 

3650 

366.8 

368.6 

370.4 

372.2 

17 

338.0 

339-8 

341.6 

343-4 

345-2 

347.0 

348.8 

350.6 

352.4 

354-2 

16 

320.0 

321.8 

323.6 

325-4 

327-2 

329.0 

330-8 

332.6 

334.4 

336.2 

15 

302.0 

303.8 

305.6 

307-4 

309.2 

311. 0 

312.8 

314.6 

316.4 

318.2 

14 

284.0 

285.8 

287.6 

289.4 

291.2 

293-0 

294.8 

296.6 

298.4 

303.2 

13 

266.0 

267.8 

269.6 

271.4 

273-2 

275.0 

276.8 

278.6 

280.4 

282.2 

12 

248.0 

249.8 

257.6 

253-4 

255-2 

257.0 

258.8 

260.6 

262.4 

264.2 

II 

230.0 

231.8 

233-6 

235.4 

237-2 

239.0 

240.8 

242.6 

244-4 

246.2 

10 

212.0 

213.8 

215.6 

217-4 

219.2 

221.0 

222.8 

224.6 

226.4 

228.2 

9 

194.0 

195-8 

197.6 

199.4 

201.2 

203.0 

204.8 

206.6 

208.4 

210.2 

8 

176.0 

177.8 

179.6 

181.4 

183.2 

185.0 

186.8 

188.6 

190.4 

192.2 

7 

158.0 

159.8 

161. 6 

163.4 

165.2 

167.0 

168.8 

170.6 

172.4 

174.2 

6 

140.0 

141.8 

143-6 

H5-4 

147.2 

149.0 

150.8 

152.6 

154-4 

156.2 

5 

122.0 

123.8 

125.6 

127.4 

129.2 

131.0 

132.8 

134.6 

136.4 

138.2 

4 

104.0 

105.8 

107.6 

109.4 

III. 2 

113.0 

114.8 

116.6 

118.4 

120.2 

3 

86.0 

87.8 

89.6 

91.4 

93-2 

95-0 

96.8 

98.6 

100.4 

102.2 

2 

68.0 

69.8 

716 

73.4 

75-2 

77-0 

78.8 

80.6 

82.4 

84.2 

I 

50.0 

51.8 

53-6 

55-4 

57.2 

59.0 

60.8 

62.6 

64.4 

66.2 

0 

32.0 

33.8 

35.6 

37-4 

39-2 

41.0 

42.8 

44.6 

46.4 

48.2 

15.55°  C.  =  60°  F. 

0 

-I 

-2 

-3 

-4 

-5 

-6 

-7 

-8 

-9 

0 

32.0 

30.2 

28.4 

26.6 

24.8 

23.0 

21.2 

19.4 

17,6 

15.8 

-I 

14.0 

12.2 

10.4 

8.6 

6.8 

50 

3-2 

1-4 

-0.4 

-2.2 

-2 

-4.0 

-5-8 

-7.6 

-9.4 

-ir.2 

-13.0 

-14.8 

-16.6 

-18.4 

-20.2 

-3 

-22.0 

-23.8 

-25.6 

-27.4 

-29.2 

-31.0 

-32.8 

-34.6 

-36.4 

-38.2 

-40°  C.  =  -40°  F. 

REFERENCES 


["  Bulletin  "  refers  to  the  publications  of  the  Div.  of  Chem.,  U.  S.  Dept.  of  Agric] 

>  J.  A.  C.  S.,  1905,  25. 

2  Bulletin  65. 

3  J.A.  C.S.,  1905,  141. 

*  Advance  sheets,  Amer.  Jour.  Pharm. 
^  J.  A.  C.  S.,  1903,  1028. 

'  Abst.  Analyst,  1900,  292. 

'  Unpublished;  to  appear  in  Chem.  Zeit. 

*  Tollens,  Handb.  d.  Kohlenh.,  2,  207. 
'  Abst.  Analyst,  1904,  306. 

•"  Z.  Anal.  C,  1905. 

"  J.  A.  C.  S.,  1904,  186. 

'2  J.  A.  C.S.,  1904,  1631. 

'3  Bulletin  65,  also  32d  Ann.  Rep.  Mass.  St.  B.  of  H.  (1900),  658. 

'*  Private  communication  to  authors. 

IS  J.A.  C.S.,  1904,  1523. 

»"  Bulletin  65. 

*^  Ding.  Polyt.  Jour.,  253  (1884),  281. 

^«  Bulletin  77. 

»»  Z.  Anal.  C,  1877,  145. 

20  Z.  Anal.  C,  1879,  69. 

2'  Ding.  Polyt.  Jour.,  233  (1879),  229. 

"  Analyst,  1891,  153. 

"  Zeit.  Anal.  C,  1879,  199. 

2*  Compt.  rend.,  35  (1851),  573. 

"  J.  S.  C.  I.,  1891,  233. 

^'  Analyst,  1895,  147. 

"  J.  A.  C.  S.,  1896,  378. 

28     T     ^^   Q^   g^ 

"  J.  C  "S.  I.,  1886,  494- 

3«  Zeit.  Anal.  C,  1877,  145- 

^'  Chem.  Anal.  Oils,  Fats  and  Waxes,  165. 

32  J.  A.  C.  S.,  1895,  935. 

33  J.  A.  C.  S.,  1903,  251,498- 

3*  Chem.  Anal.  Oils,  Fats  and  Waxes. 

35  J.  A.  C.S.,  1900,453;   1901,  I. 

3'  Chem.  Anal.  Oils,  Fats  and  Waxes,  574. 

3'  Much  misrepresentation  has  been  made  of  this  matter.  Several  American 
chemists  have  ignored  our  claims  to  the  devising  of  the  process.  The 
Gerber  method  is  merely  a  modification  of  it.  This  fact  is  known  to 
chemists  of  the  Department  of  Agriculture  at  Washington,  yet  in  the 
"Provisional  Methods  of  Food  Analysis,"  the  Gerber  method  is  men- 
tioned as  an  alternative,  as  if  it  were  entirely  original  with  Gerber. 

389 


390  REFERENCES 

''  J.  A.  C.  S.,  1899,  503. 

39  J.A.  C.  S.,  1904,  1195. 

*°  J.  A.  C.  S.,  1904,  1195. 

*^  Russky  Vratch.     Abst.  Jour.  Am.  Med.  Ass'n.,  44  (1905),  1235. 

"  J.  A.  C.  S.,  1900,  207. 

*^  Stokes    &  Bodmer  suggested  10  minutes'  boiling,  but  Watts    &  Tempany 

(Analyst,  1905,  119)  show  that  at  least  30  minutes'  boiling  is  necessary. 
**  Bulletin  65. 
«  J.A.  C.  S.,  1905,270. 

*^  Mikroscopie  der  Nahrungs-  und  Genussmittel. 
*''  Food  Adulteration  and  its  Detection. 
*^  Bulletin  13. 

*^  Rep.  State  Board  of  Health  of  Mass.,  1902,  485. 
^°  Winton,  Bulletin  65. 

^'  Rep.  State  Board  of  Health  of  Mass.,  1903. 
^2  J.  A.  C.  S.,  1899,  721. 
^^  Brooks,  Rep.  Lab.  Hyg.  N.  J.,  1903. 
'*  J.  A.  C.  S.    1899,  257. 
^^  J.  A.  C.  S.,  1902,  1129. 
^^  Food  Inspection  and  Analysis,  in  place. 
"  Bulletin  65. 
^^  The  reference  {Chemist  &*  Druggist,  57,  732)  directs  the  use  of  "25  per 

cent,  sulfuric  acid."     It  is  assumed  that  proportion  by  weight  is  meant. 
59  Rep.  State  Board  of  Health  of  Mass. 

«°  J- A.  C.S.,  1901,349. 

«i  J.A.  C.S.,  1905,613. 

*^  Leach,  Food  Inspection  and  Analysis,  261. 

«3  Bulletin  65. 

«*  Bulletin  64. 

«5  J.A.C.S.,  1905,  137. 

««  J.  A.  C.  S.,  1905,  138. 

"  J.A.  C.S.,  1903,16. 

°^  Analyst,  1904,  301. 

89  Edition  of  1890. 

'»  J.  A.  C.  S.,  1904,  1627. 

'^  Analyst,  1905,  124. 

^2  J.  A.  C.S.,  1900,810. 

^3  Allen's  Com'l  Org.  Anal.,  i,  in  place. 

'*  Allen's  Com'l  Org.  Anal.,  i,  in  place. 

'^  Amer.  Chem,  J.,  1899,  266. 

'8  Analyst,  1904,  301. 

"  J.  A.  C.  S.,  1904,  1086. 

"  Bulletin  65. 

79  Bulletin  65. 

8°  Bulletin  65. 

^^  Bulletin  65,     Some  errors  in  the  Bulletin  description  have  been  corrected 

here. 
^^  Com'l  Org.  Analysis,  vol.  4. 
*3  J.  A.  C.  S.,  1904,  662;   also  Fresenius'  Quantitative  Anal.,  Amer.-Ed.,  1904. 


INDEX 


Abrastol,  77,  86,  220 
Acetyl  number,   156 

value,   156 

Acidity,  total,  359 
Acid  mercuric  iodid,  229 
nitrate,  2 1 


value,  146 

Acorn  starch,  90 
Acrinyl  isothiocyanate,  317 
Adams'   method,   201 
Agar,   334 
Albumin,  190,  208 
Albuminoid  nitrogen,  37 
Alcohol,  detection,  352 

determination,  353 

ethyl,  54 

methyl,  54 

detection,  365 


— tables,  354-5-6 

Alcoholic  beverages,  337 
Ale,  343,  344 
AUihn's  method,   117 
Allspice,  311 
Allyl  isothiocyanate,  317 
Almen's  reagent,  208 
Alum  in  bread,   102 

in  flour,  97 

Alumina-cream,   118 
Aluminum  acetate,  378 

detection,  378 

determination,  386 

Ammonium  in  baking  powders. 
Amphoteric  milk,   192 
Annatto,  detection,  215,  217 
Antisepticum,  79 
Apparatus,  49 
Arachidic  acid,   175 
Arachidin,  174 
Arachis  oil,  174 
Arnold's  method,  36 
Arrow-root  starch,  89,  92 
Arsenic,  detection,  60-62,  220 
Asaprol,  86,  87,  220 


109 


Ash,  39 
Azolitmin,  55 


Babcock's  method,  200 
Baking  powders,  107 

soda,  105 

Banana  starch,  89 
Barley,  97,  100 

starch,  90,  92 

Bases,  meat-,  382 
Baudguin's  test,  167 
Bean  starch,  90,  92 
Bechi's  test,  166 
Beef  fat,  188 

stearin,  186 

Beer,  343 

root,  343 

Benzoates,  76,  81 
Benzoic  acid,  76,  81 
Birotation,  213 
Bitters  in  beer,  366 
Biuret  reaction,  385 
Bjorkland's  test,  180 
Boiled  milk,  detection,  220 
Boiling-point,   12 

Borax,  78,  82,  239 
Boric  acid,  78,  82 
Borofluorids,  78,  82 
Brandy,  341 
Bread,  loi 

commercial,  102 

Bromas,  277 

Bromin,  thermal  value,  149 
Brulle's  test,  168 
Buckwheat,  97,  100 

starch,  91,  92 

Bumping,  prevention,  44,  45 
Burners,  51,  52 
Butter,  230 

cacao-,  179 

colors,  237 

composition,  230 


391 


392 


INDEX 


Butter  fat,  189 
milk,  193 

peanut,  174 

vegetable,  179 

Butyrorefractometer,  154 


Cacao,  273 

butter,  179 

essence,  277 

husks,  277 

masse,  277 

red,  275 

starch,  90 

Caffearin,   262 
Caffein,  253,  257 

determination,  257 

Caffeol,  262 

Caffetannic  acid,  267,  292 
Calculation  methods   for  milk,    204 
Candies,  135 

Cane-sugar,   121 
Canna  starch,   89 
Caper  tea,   256 
Caramel,  124,  362 
Caryophyllin,   315 
Casein,   190,   208 
Cassia,  313 

oil,  314 

Catsup,  S33 
Centrifuge,  50,  203 
Cereals,  95 

starches,  91 

Champagne,  346 
Cheese,  240 
Chemicals,  49 
Chicory,  266 
Ching  suey,  256 
Chocolate,  273 

nuts,  276 

Cholesterol,  160 
Chromium,  detection,  58 
Cider,  337 

vinegar,  284 

Cinnamon,  312 

oil,  314 

starch,  91 

Citric  acid,   determination,  in  milk, 

191 
Clove  oil,  315 
Cloves,  315 

Cobalt  nitrate  test,  no 
Cochineal,  56,  72 
Cochran's  method,  224 
Cocoa,  277 


Cocoas,  soluble,  277 
Coconut  oil,  178 

olein,  179 

stearin,  1 79 

Coffee,  262 

essence,  272 

extracts,  272 

Colors,  64-75 

in  butter,  237 

in  candies,  136 

in  meat,  377 

in  milk,  215 

in  wine,  361 

test  for  oils,  137 

Colostrum,   195 

Colza  oil,   178 
Condensed  milk,  222 
Condensers,  45-8 
Condiments,  282 
Confections,   135 
Congou  paste,  256 

tea,  256 

Constants  for  oils,  164,  165 
Copper,  detection,  59 

hydro xid  mixture,  37 

in  bread,  104 

in  flour,  98,  104 

Coriander  seed,  301 
Corn,  Dhoura,  301 

meal,  97,  100 

oil,  172 

starch,  91,  92 

Cottonseed  oil,  171 

stearin,  172 

Cream,  193 

evaporated,  222 

of  tartar,  105 

Cribb's  condenser,  45 
Crude  fiber,  38 
Cryoscopy  of  milk,  214 
Cumarin,  324 


Dalican's  titer  test,  11 
Desserts,  335 
Dextrin  in  honey,  131 

in  wine,  359 

Dextrose,  determination,  113 
Dhoura  corn,  301 

starch,  90 

Distillation,  44 
Doughing  test,  96 
Drying  of  oils,  154 
ovens,  28,  30 


INDEX 


393 


Drying  property,  154 
Dry  wine,  346 


Egg  colors,  72 

detection,  335 

Elaidin  test,  152 

Electrolytic  methods,  1 1 6 

Ergot,  98 

Erucin,   178 

Essence  of  cacao,  277 

of  coffee,  292 

Ether  purification,  54 
Eugenic  acid,  315 
Eugenol,  315 
Evaporated  cream,  222 
Extract,  27 
Extraction  apparatus,  41 


Facing  coffee,  264 

tea,  258 

Fat  of  milk,  190,  200 
Fats,   137 

Fehling's  solution,  113 
Fermented  milk,  248 
Fiber,  crude,  38 
Inlter-tubes,  114,  115 
Fixed  solids,  27 
Flesh-foods,  373 
Flour,  93,  97 
Fluorescence,  23 
Fluorids,  78,  82 
Foreign  leaves  in  tea,  260 
Formaldehyde,  77,  83,  218 
Formalin,   77 
Fractional  distillation,  49 
Furfural  test,  167 
Fusel  oil,  determination,  363 


GaLACTOSAZONE,    III 

Gallisin,  125 
Gelatin,  detection,  217 
Gin,  341 
Ginger,  306 

starch,  89 

Gingli  oil,  177 
Gliadin,  95 
Globulin,  95 
Glucosazone,   in 
Glucose,  125 
Glutenin,  95 
Gluten  test,  96 
Glycerol  in  wine,  350 


Glycerol  soda,  143 
Glycogen,  375 
Graham  flour,  97 
Grape-juice  vinegar,  283 
Grape-sugar,   125 
Gum  in  wine,  359 
Gutzeit's  test,  61 
Gypsum  in  bread,  104 


Hager's  test,  352 
Halphen's  test,   166 
Hanus'  reagent,   140 
Hehner  value,   155 
Honey,  130 

Horseflesh,  detection,  375 
Hiibl's  reagent,  139 
Hydrometers,  6 
Hydronaphthol,  77 


Ice-cream,  335 
Immiscible  solvents,  43,  55 
Improvers,  meat,  378 
Index  of  refraction,  153 
Indicators,  55 
Indigo,  detection,  258 
Insoluble  acids,   155 
Inversion  methods,  119,  227 
Inverted  condenser,  48 
Invert-sugar,  119,  227 
lodin  number,  139 

value,  139 

Iron,  detection,  58 

Jams,  327 
Jellies,  327 

Kefyr,  249 
Kjeldahl-Arnold  method,  36 

Gunning  method,  32 

Kottstorfer  number,  145 
Kumiss,  248 

LACTOSAZONE,    III 

Lactose,  no,  in,  191,  210 

Lager  beer,  343,  344 

Lard,  180 

Laurent  polarimeter,   13 

Laureol,  179 

Laurin,  178 

Lead,  detection,  58 

subacetate,  118 


394 


INDEX 


Leavening  materials,  105 
Leffmann-Beam  method,  203 
Leguminous  flours,  99 
Lemon  extract,  324 

juice,  330 

—  sirup,  330 

Lentil  starch,  90 
Lieben's  test,  352 
Lie  tea,  256 
Lignoceric  acid,   175 
Litmus,   55 
Livache's  test,  154 
Long  pepper,  301 
Low  wine,  283 


Mace,  308 

false,  309 

Maize,  97,  100,  104 

oil,  172 

starch,  91,  92 

Malic  acid,  290 

value,  129 

Malt  extract,  93,  371 

liquors,  342 

vinegar,  285 

Maltosazone,  in 
Maple  sugar,  127 

sirup,  127 

Maranta  starch,  89 
Marsh's  test,  62 
Maumene's  test,  148 
Mead,  343 

Meal,  93 

Meat  bases,  382 

extracts,  382 

Meats,  373 
Melting-point,   7 
Mercuric  iodid,  acid,  229 

nitrate,  acid,  211 

Metals,  poisonous,  57 
Methyl  alcohol,  54 
detection,  365 


orange,  56 


Microscope,  23 
Milk,  190 

ash,  191,  200 

• — boiled,  193,  220 

condensed,  222 

enzyms,   191 

— ■ serum,   193 

• sugar,  191 

Miscible  solvents,  41 
Mixed  flours,  99 
Mohr's  centimeters,  20 


Molasses,  123 
Mother  cloves,  315 

starch,  89 

Must,  348 
Mustard,  317 

oil,  317 

Myristic  acid,  308 
Myristicol,  308 
Myronic  acid,  317 
My  rosin,  317 

Naphthol,  77,  85 
Nickel,  detection,  58 
Nitrogen,  albuminoid,  37 

total,  32 

Normal  weight,  20 
Nucoline,   179 
Nutmeg,  307 

starch,  90 

oil,  307 


Nutshells,  300 


Oats,  97,  99 
Oat  starch,  91,  92 
Oil,  arachis,   174 

cassia,  314 

cinnamon,  314 

cloves,  315 

coconut,  178 

colza,  178 

corn,  172 

cottonseed,  171 

gingli,  177 

maize,  172 

mustard,  317 

nutmeg,  307 

olive,  168 

peanut,  174 

pepper,  293 

rape,  178 

sesame,  177 

teel,  177 

Oleomargarin,  232 
Oleorefractometer,  153 
Olive  oil,  168 

stones,  298 

Original  solids,  287 
Ovens,  28,  30 


Paraffin  in  oleomargarin,  240 
Peanut  butter,   174 
oil,  174 


INDEX 


395 


Pea  starch,  90 
Penumbral  polarimeters,  13 
Pepper,  293 

cayenne,  304 

long,  302 

starch,  91 

Pepperette,  298 

Peptones,  determination,  383 

Perry,  337 

Petroleum  spirit,  55 
Phenol,  85 
Phenolphthalein,  56 
Phenylhydrazin  test,  1 1 1 
Phytosterol,  161 
Pintus,  A.  S.,  86 
Piperidin,  293 
Piperin,  293 
Plastering  of  wine,  350 
Platinum,  care  of,  53 
Poisonous  metals,  57 
Poivrette,  298 
Polarimetry,  13 
Porter,  344 
Potato  flour,  99 

starch,  89,  91,  92 

Preservaline,  78 
Preservatives,  76,  378 
Process  butter,  236 
Proteids,  determination,  205 
Proteoses,  determination,  383 
Prune  juice,  detection,  362 
Prussian  blue,  detection,  258 
Putrefaction,  detection,  378 
Pyknometer,  2 


QuERCiTANNic  acid,  312 


Rape  oil,  178 
Reagents,  25,  52 
Recknagel's  phenomenon,  192 
Refraction  index,  153 
Refractometer,  153 
Reichert-Meissl  number,  143 
Reichert  number,  143 
Reinsch's  test,  60 
Renovated  butter,  236 
Rex  magnus,  78 
Rice  starch,  91,  92 
Ritthausen  method,  207 
Root  beer,  343 
Rum,  341 
Rye  flour,  96,  99 
starch,  90,  92 


Saccharin,  77,  80,  361 

Sago  starch,  90 

Salicylic  acid,  76,  80,  362 

Salol,  85 

Saponification  equivalent,  146 

value,  145 

Sausage,  adulteration  of,  378 

Sawdust  in  flour,  100 

Scales  for  polarimeter,  20 

Scheibler's  method,  21 

Schmidt  and  Hiinsch  polarimeter,  15 

scale,  20 

Separated  milk,  193 
Sesame  oil,  177 
Silicofluorids,  78,  82 
Sirup,   123 
Sitosterol,   161 
Sodium  benzoate,  76 

phosphomolybdatc,  274 

Solidifying-points,  7 
Solids,  original,  287 
Soluble  acids,  155 

cocoas,  277 

Solvents,  immiscible,  43,  55 

miscible,  41 

Soxhlet's  method,  210 
Specific  gravity,  i 
bottle,  2 


rotatory  power,  19 

temperature  reaction,  148 

Spectroscope,  21 

Spices,  291 

Spirits,  338 

Sprengel  tube,  3 

Standard  acid,  56 

Stannous  chlorid  in  bread,  105 

in  sugar,  122 

Starch,  87 

detection,  87 

determination,  93 

indicator,  56 

Starches,  characters  of,  89,  90,  91 

I  Stearin,  beef,  186 

coconut,  179 

cottonseed,  172 

Stout,  343 

Stutzer's  method,  37,  246 

Sublimation,  44,  49 

Sucrose,  121 

Sugar,  cane-,  no 

Sugars,  no 

Sugar  scale,  20 

Sulfites,  78,  359 

Sulfur  chlorid  test,  186 

Sulfuric  acid  in  vinegar,  289 


396 


INDEX 


Sulfurous  acid  determination,  360 
Szombathy's  tube,  45 

Table  accessories,  ^;^^ 

Taenia,  forms  of,  381 

Tallow,   187 

Tannin,  determination,  292 

Tapeworm,  381 

Tapioca  starch,  90 

Tartaric  acid,  332 

Tea,  252 

Teel  oil,  177 

Terra  alba  in  bread,  104 

Thein,  253 

Theobromin,  273 

Thermal  reactions,  148-150 

Tin,  detection,  58,  59 

in  bread,  105 

Titer-test  in  sugar,  122 
Tocher's  test,   168 
Treacle,   123 
Trichina,  381 
Turmeric,  310 
starch,  89 

Ultramarine  blue,  122 
Unsaponifiable  matter,  159 

Valenta's  test,  147 


Vanilla  extract,  320 
Vanillin,  323 
Vegetable  butter,  179 
Vegetaline,   1 79 
Vinegar,  282 

cider,  284 

malt,  285 

spirit,  285 

wine,  283,  284 

Viscosity,   158 
Volatile  acids,   142 

Water  determination,  27 

specific  gravity  of,  386 

Weissbier,  343 
Werner-Schmid  method,  202 
Weston  distillation  apparatus,  45 
Westphal  balance,  4 
Wheat,  96,  99 

starch,  90 

Whey,  193 
Whiskey,  339 
Wild's  scale,  21 
Wine,  345 

low,   283 

vinegar,  283 

Wool  test,  64 

Zinc,  detection,  58,  59 


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